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Canon EOS Beginners’ FAQ

PhotoNotes.org DonationsCopyright © 2002-2007 NK Guy

Version 0.9.5. 6 January, 2007.

http://photonotes.org/articles/beginner-faq/

Part V - Filters.

I bought a filter. Do I have to adjust something on the camera to use it properly?

Most SLR cameras, such as all Canon EOS cameras, do their metering directly through the lens. So if you put something like a filter in front of the lens you don’t need to compensate manually at all. The filter reduces the amount of light entering the camera, of course, but the camera still meters through the lens as it always would. So it works just fine.

There are at least three special case scenarios where this is not strictly true, however. None of these are typical situations encountered by a beginner, but here they are for completeness:

1) If you use a handheld light meter (a separate device from the camera) instead of the camera’s built-in light meter then you will obviously need to compensate for the presence of a filter.

2) If you use a linear polarizing filter rather than a circular polarizing filter you may experience errors in the metering and autofocus system. Then again, you may not. But best play it safe - when buying a polarizing filter for your camera buy only circular polarizers, sometimes identified as CPL filters.

3) If you are doing specialized infrared photography using a black filter which blocks visible light but which lets infrared energy pass through the camera’s internal meter is likely not to work very well, since camera meters are designed with visible light only in mind.

My camera salesperson tried to sell me a protective filter. Should I get one?

This is another question with a yes and no answer. There are two schools of thought regarding clear glass or UV-blocking protective filters. Some photographers use them to reduce the risk of damage to the lens - if you bash your lens against the wall then having a filter lowers the risk of the lens itself suffering damage. Other photographers refuse to use them on the grounds that any extra glass on the end of the lens, no matter how good, degrades image quality.

So there are a number of points here. First, there’s nothing utterly essential about “protective” filters. You’re simply lowering the risk of lens damage by using one. Second, if you get a UV filter to serve as lens protection try to get the best quality you can afford and keep it assiduously clean. A cheap or dirty filter will degrade the quality of your photos dramatically. Third, remember that camera salespeople earn big commissions by selling you little accessories like this - don’t necessarily buy whatever they’re trying to push on you. Chances are they’re trying to sell you a piece of junk that happens to earn them a bigger commission. Fourth, using a filter doesn’t mean you don’t have to use a lens hood. In fact, in the case of lenses with slightly recessed front elements, putting a filter on means you’re going to run a greater risk of lens flare than without. Always use a hood.

Now, having said all this about theory, my views on using a filter on a lens changed last year somewhat. I was in Tunisia and taking some photographs in an old Roman amphitheatre. I didn’t have a lens on my camera, had the hood off temporarily and somehow banged the lens against a stone column or something. The front element on the lens got badly scratched and gouged. If I’d had a filter or a lens hood in place then I’d still have a usable lens. As it is I have’t, since getting a replacement front element from Canon is half what the lens if probably worth these days.

For more information on filters in general, have a look at my filters page.

Should I buy a coated or an uncoated filter?

Nearly all lenses sold today for 35mm SLRs are coated with optical coatings that are designed to reduce internal reflections. This is pretty critical for image quality - particularly contrast and flare. Some filters are monocoated, some are multicoated, and some aren’t coated at all.

The argument in favour of coatings is pretty straightforward. You’ve got coated lenses - why spend money on putting uncoated glass in front of them? Regular filters mean you’re putting two reflective surfaces in front of your lens. Surely you should go for the best image quality and get coatings.

The arguments against are that coated filters are harder to clean and easier to scratch. These are both demonstrably true. Fingerprints show up much more easily on coatings, and getting that fine layer of greenish shimmering finger oil off a coated surface can be a real pain. And some coatings are indeed easy to scratch.

Personally I go for multicoated filters for the most part. I buy the “reduce reflections” argument - I’ve had a few pictures suffer from lens flare - one from a really bad internal reflection - caused by uncoated filters. As for cleaning, yes. It is a pain. But keeping your lens clean is important for image quality regardless. And I try to keep the filters in their cases when they’re not being used to minimize the chances of coating damage.

What does a polarizing filter do?

Light moves through space, vibrating as waves in many different directions. Light which is polarized, however, only vibrates in one plane. A polarizing filter or “polarizer” is a lens filter which polarizes light along one plane. This can cut non-metallic reflections and enhance contrast under certain conditions.

Polarizing filters contain a layer of polarizing material which is laminated between two glass circles and mounted in a frame. You can then rotate this filter, which affects the amount of light passing through. Even at their “brightest” setting, however, polarizing filters reduce the amount of light entering the lens - they always cost a stop or so of light.

So what use are they? Well, polarizers are useful for cutting reflections from water and glass (ie: non-metallic) surfaces. They’re commonly used for cutting reflective glare off of windows, or for taking a photo of a lake without a reflection on the lake surface, for instance. They can also be used to darken blue sky (technically, increase the colour saturation of the sky since light scattered by Rayleigh scattering is polarized) and certain types of vegetation. The effect of a polarizer on the sky varies depending on the angle to the sun (known as Brewster’s angle). So a very wide-angle lens (wider than 24mm or so) with a polarizer will demonstrate differing amounts of polarizing across the frame, which may or may not be objectionable.

There are two basic kinds of polarizers - linear and circular. Linear polarizers work well with manual focus cameras, but they interfere with autofocus cameras. Circular polarizers contain another element - a “quarter wave” plate - which ensures compatibility of the filter with autofocus systems. So if you’ve got an autofocus camera - like any EOS model - be sure to use only circular polarizing filters. Note that polarization is one of the few visual effects provided by filters which strictly speaking can’t be simulated digitally in an image editing program.

What common filter sizes do Canon employ?

Like most Japanese camera makers, Canon use threaded (screw-on) filters with metric measurements on most of their lenses. The exceptions are those lenses with very large front elements that are too big to accept threaded filters - the super-wide angle lenses and the really huge telephotos. These use internal drop-in filters instead.

Canon have standardized their filters to a common set of sizes. The sizes used by Canon are typically:

With the exception of the 67mm filter lenses it’s convenient that Canon have relatively few filter sizes, as it means you can invest in a good selection of filters for each type of lens that you own, and minimize the number of different sizes you carry with you.

Of course, if you have infrequently used larger filters you can use step rings to adapt them to smaller lenses. So if you rarely use a red filter, for example, you might buy a 72mm one and then adapt it to your 67mm filter size lens when needed.

What is a neutral density filter?

Neutral density (ND) filters are simply filters which block a certain percentage of light from passing through. In other words, they’re darkening filters. The “neutral” refers to the fact that a proper ND filter does not colour the light inadvertently. (ie: a true neutral density filter does not introduce any colour casts to the image)

Such filters are useful for, for example, shooting outdoors in bright sunlight when you happen to have fast film. They’re also handy for extending shutter times. For instance, nature photographers often like shooting waterfalls or moving water with very long shutter times in order to achieve the bridal veil effect of blurring motion. To do this with ordinary film requires an ND filter to cut back the amount of light hitting the film. Users of mirror lenses also use ND filters in the unusual case that they need to cut back on light, since mirror lenses lack adjustable aperture diaphragms.

ND filters are typically specified in either decimal values or numeric factors. 0.3 ND filters cut 2X the light entering, 0.6 ND filters cut 4x the light entering, 0.9 ND filters cut 8x the light entering, and so on.

What is a graduated neutral density filter?

A graduated neutral density filter is a specialized type of neutral density filter. Such a filter has a dark side and a clear side with a smooth transition line between the two. Such filters are useful for taking photos of scenes where one half is bright and the other less so.

For example, a classic case where GND filters are useful is that of a sunset. Light from the setting sun isn’t as bright as the noonday sun but is still too bright for the range of film to accommodate. So if you meter to get the sky right then the ground or ocean portion of the photo will be wildly underexposed and look like a dark blob. But if you meter for the darker section then the sky will be completely blown out and overexposed. The answer is to use a graduated neutral density. You position the filter such that the darker section darkens (“holds back”) the sky and the clear section is over the non-sky areas. You then expose for the darker area and the bright area will come through beautifully.

GND filters come in varying densities and also with hard or soft transition lines. Hard lines offer a fairly sharp transition between the dark area and the clear area and are useful for sky and ocean shots, etc. Soft lines offer gradual transition and so disguise the transition better for landscapes and the like. Unfortunately there is no standard for the distance over which this transition takes place, so each filter maker has its own idea as to what is a hard or soft transition.

Is putting more than one filter onto a lens okay?

This is a practice known as stacking filters. And generally it’s probably not a good idea since the risk of vignetting goes up. By putting more and more filters on the end of your lens you’re essentially making your camera look through a long tube. In addition each piece of glass you add has the potential to degrade image quality further.

Unless you really need to put two filters onto your lens to achieve a certain effect it’s probably wise to stick with just one at a time.

Do I need a slimline filter for my wide angle lens?

Wide angle lenses are more susceptible to the problem of vignetting than other types of lenses. For that reason filter makers often make low-profile or slimline filters for use with wide angle lenses. Such slim filters may lack a front filter thread, so they may require press-on lens caps rather than normal ones. They also tend to cost more.

In my experience with a number of Canon lenses you can safely put any normal filter on Canon wide-angle lenses (I’ve used up to 20mm) without fear of vignetting. Obviously cheap filters with gigantic high-walled metal rings might be a problem, but typical Hoya or B+W filters haven’t been a problem for me. Now, your mileage may vary, as they say. So it’s probably wise to do a quick test if possible - take photos of the sky at different aperture settings to see if there’s any darkening around the edges with and without the filter. But I wouldn’t automatically assume you need to buy a costly slimline filter unless, perhaps, you like stacking filters.

I have filters which don’t fit my lenses. Can they be adapted?

Yes. You need what are known as step rings - simple machined metal adapter rings which fit between the filter and the lens. Such rings are fairly inexpensive and readily available from camera shops.

If you have a large filter and want to attach it to a lens with a smaller filter diameter (eg: a 72mm filter on a lens with a 58mm filter thread) then you need a step-up ring. If you want to go from a small filter to a larger lens you need a step-down ring.

Adapting filters in this fashion often works fine but there are some points to keep in mind. First, attaching a small filter to a larger lens will usually result in vignetting - darkening around the edge of the photograph. The smaller the filter the higher the likelihood of vignetting. Second, attaching larger filters to smaller lenses often poses problems when you try to attach a lens hood. The filter might prevent the lens hood from fitting or might make it inconvenient to rotate polarizers, etc.

Naturally, the closer the filter and lens are in size the better. Using 58mm filters on 52mm lenses is rarely a problem, for example. Step rings are thus handy for minimizing the number of filters you have to carry around for a given lens set.

What are these numeric codes on my filter?

Unfortunately there is no universal specification for filter types. Luckily filter thread types are pretty well standard across all major Japanese camera makers, but filter colour and type are named on a manufacturer-specific basis.

There are two common systems in use, however. Most American and British filters are specified using Wratten numbers, an arbitrary series of numbers and letters created by UK photographer Frederick Wratten. And German and Scandinavian filters tend to be use a different system which include K (warming) and B (cooling) filters.

What about Cokin filters?

Ah, Cokin filters! Delightful rectangles of plastic sold by the millions during the heyday of amateur photography in the 1970s! No matter what cheesy effect you want - lurid pink skies, prismatic highlights, simulated motion blur - Cokin can help you! Every camera shop has a dusty rack in the corner laden with Cokin filters.

Personally I think they’re pretty expensive toys, particularly given that they’re just uncoated pieces of plastic resin. Photoshop has far surpassed Cokin’s ability to alter images, and it does so in a far more flexible and versatile fashion. Cokin’s P holder is useful as a standard filter holder compatible with wide-angle lenses (particularly if you saw off the outer two slots), though many people eschew Cokin’s “grey” graduated filters as they aren’t true neutral density filters and can lend subtle but unwanted colour casts. But frankly the day of these novelty filters has come and gone. Unless you still shoot exclusively on film, digital has made these filters largely irrelevant.

Why do black and white photographers use such brightly coloured filters?

Colour filters can achieve a variety of effects in black and white photography. They work by passing light that’s the same colour as the filter and blocking much of the light that’s the complementary colour. For example, a red filter lets lots of red light through but blocks blues and greens.

What does this do on black and white film? Well, such colour filters have the effect of brightening areas in a photo of their own colour and darkening areas of their complementary colours. So, our red filter will make a red T-shirt look almost white and a blue sky look dark grey or almost black. It’s for this latter purpose that red filters are commonly used in black and white photography - they can be used to darken skies dramatically and smooth skin tones of lighter-skinned people.

This effect of sky darkening is particularly useful when there are clouds. Clouds and sky are often the same brightness on black and white film, which means that clouds can end up disappearing in the final photo. By using a red filter, however, you can darken the sky in order to heighten the contrast between the sky and clouds.

The main drawback of such colour filters is that they decrease the overall amount of light entering the camera. You don’t have to adjust for this if you’re using the camera’s built-in light meter, but it does mean that you will need slower shutter speeds than if you didn’t use the filter at all.

My pictures suck. I want to attach a magic filter to my lens to make them look great.

There is no such device.

Generally speaking, good photos tend to result from, in varying degrees, a good eye, good technique, good understanding of lighting, quality lenses, experience and luck. And you don’t even necessarily need a quality lens, though they can obviously help a lot if you want to take a sharply focussed or high-contrast image.

VI - Miscellaneous questions.

Taking pictures.

The edges of my photos are dark. What’s going on?

This is a problem known as vignetting (though it’s technically sometimes peripheral darkening, which looks pretty well the same in the final photo), and has several possible causes.

How can I get the sharpest photos possible using my equipment?

What is the handholding rule for non-blurry photos when not using a tripod?

Taking photos with the camera mounted firmly on a tripod will always yield sharper pictures than if you were to hold the camera in your hand. No matter how steady you are you’ll always move slightly during even a split-second exposure. You can mitigate this somewhat through a variety of means - bracing yourself, pressing the shutter release gently rather than jabbing it, trying to lean against a wall or a fence, holding your breath or gradually exhaling as you take the photo, using an image stabilized lens, and so on. But despite all these things a tripod is a safer bet.

However, tripods are obviously a nuisance to use much of the time. And if the shutter speed of the camera is high enough then camera blur shouldn’t be too bad. The question is, how high a shutter speed is fast enough?

There’s a basic rule of thumb in photography which says that you shouldn’t use a shutter speed slower than the reciprocal of the focal length value. That sounds complicated, but it’s actually really straightforward.

Let’s say you’re using a 50mm lens. The reciprocal of 50 is 1/50. So you shouldn’t use a shutter speed any slower than 1/50 of a second when handholding a 50mm lens. Of course, most cameras don’t have a 1/50 sec setting, so you round it up to 1/60 second.

It’s as simple as that. Put the value of the current focal length as the denominator of a fraction with 1 as the numerator. When using a zoom lens use whatever focal length the zoom is currently set to.

Now you’ll notice two important consequences of this rule. First, it means that when you’re using long telephoto lenses you have to have relatively high shutter speeds. A 300mm lens, for example, requires at least a 1/300 sec exposure. Second, it means that you can get away with relatively slow shutter speeds when using a wide angle lens. A 15mm fisheye lens, for example, lets you use 1/15 second.

Of course, this rule is modified somewhat if you have image stabilization (IS) on your lens. IS lets you gain at least an additional two stops of shutter speed.

Now technically this rule of thumb is about determing the minimum shutter speed for a given field of view. By coincidence it just works out fairly well if you use the lens focal length when shooting 35mm film.

Do I really need a tripod? They’re such a pain to haul around.

Yes, they are a pain. Good tripods in particular are heavy and clumsy to carry. But they’re often the best way to take a sharp, clear photograph by providing a stable, relatively vibration-free platform. If image sharpness is important to you - as it is for studio photography and nature photography, for example, you need a tripod. And of course they’re pretty well essential for night photography, where long exposure times (often many seconds or minutes) will cause hopelessly blurred photos if you try to handhold the shot. Try to get the heaviest one you can reasonably carry as lightweight ones vibrate too much, and consider investing in a quick-release head as the added convenience means you’ll probably end up using it more.

Obviously tripods aren’t an appropriate tool for candid or street photography where you need to move quickly, so this isn’t an absolute rule. If you can’t use a full-sized tripod try anything else that helps increase camera stability. For example, monopods are simple telescoping poles with camera mounts on the end. They’re popular with some photographers as they’re quite lightweight and portable, yet stabilize the camera in one direction (vertical) and help minimize movement in the other (horizontal). Some monopods even double as high-quality hiking or trekking poles, making them useful for rugged nature photography.

Another option is a tiny folding tabletop tripod sturdy enough to support the weight of your camera and largest lens. Such tripods can be used on flat surfaces like tables and car roofs quite effectively. Some even have velcro straps so the small tripod can be strapped firmly to a tree trunk or a fence.

Other options for camera stabilization abound. Beanbags are popular accessories for shooting out of car windows or when lying on the ground. Chainpods are simply lengths of metal chain (or non-stretchy rope) attached to the tripod mount. The end of the chain dangles to the ground, allowing you step on it and pull the camera up for stability. You can even get shoulder stock mounts with triggers which let you shoot your camera as if it were a rifle, though such devices are obviously highly unwise if you’re taking photos of political figures or people in public. And so on.

My camera doesn’t fit my tripod. The bolt is the wrong size. What can I do?

The vast majority of cameras sold today use a 1/4-20 tripod mount socket. This means that the bolt which fits into it is 1/4 inch in diameter and has 20 threads per inch. Even European and Japanese cameras and tripods use these non-metric measurements for historical reasons. Conveniently, most tripod heads also use the 1/4-20 size.

However, some tripod heads and some larger cameras use a 3/8-16 bolt size. If you need to go from one to the other you can purchase bushings which fit into the larger hole, though for some incomprehensible reason these bushings are often sold in unhelpfully large packages, such as 25 to a pack. You can also buy adapters.

Note that since cameras use standard 1/4-20 sockets it’s very easy to make your own homemade camera stand or tripod mount. 1/4-20 bolts are commonly available in hardware stores (though it may take some searching if you’re outside the UK and North America). However, remember that the hole itself isn’t very deep. If you try to force a bolt too far into the camera body you could seriously damage your camera. Especially if your camera has a plastic tripod mount, as most low-end cameras do. For that reason you should test the length of the mounting bolt very carefully.

What is the sunny 16 rule?

The sunny 16 rule is a simple rule of thumb for taking photos in daylight without a light meter. The rule is quite easy to remember - if you’re taking a photo in bright daylight set the aperture to f/16 and set the shutter speed to be as near as possible to the reciprocal (1 / x) the film speed.

So if you’re using ISO 100 film, for example, you would set the aperture to f/16 and the shutter speed to 1/100 sec. However, since most cameras don’t have a 1/100 sec setting you would set it to the closest shutter speed, which is 1/90 sec.

If you want to use a different aperture calculate the number of stops away from f/16 you want to use and then adjust the shutter speed accordingly. For example, f/11 is one stop larger than f/16, so you’d need to decrease your shutter speed by one stop. So if you’re using ISO 100 film you’d set the aperture to f/11 and the shutter speed to 1/200 sec.

This rule works from many locations on the Earth because the light output from the sun is a pretty constant value - the sun itself puts out a nearly constant amount of light at all times. Only precisely calibrated equipment can detect the light fluctuations of the sun.

What is the rule of thirds?

The rule of thirds is the compositional guideline (it isn’t strictly a rule per se) which states that images with dominant points of interest usually look best with those points situated about 1/3 of the way along the image.

For example according to this guideline a horizon looks best 1/3 of the way down from the top of the image or 1/3 of the way up from the bottom. Or a picture of a field with a large tree in it will look best when the tree is situated roughly 1/3 of the way across the image from one edge. It’s a useful starting point for composition, especially if you’re a beginning photographer. A common novice mistake is to centre everything and try to get things right in the middle, which often results in rather static-looking photos.

This guideline is essentially a simplification of the golden section or golden mean.

I took a photo and the sky is white. Why is this, when the sky was actually blue at the time?

The basic problem is this: the human eye is capable of sensing a pretty wide range of light levels. Film and digital image sensors, however, are not.

So let’s say you take a photo of something and your camera meters off the foreground to expose it correctly. If there’s a fairly wide range of brightness between the sky and the ground then metering for the ground will cause the sky to be vastly overexposed. And if it’s overexposed then it’ll appear “blown out” or pure white - it’s as bright as the film or sensor are capable of recording.

The same problem occurs at sunset. A common beginner experience is to take a photo of a glorious sunset and to be utterly disappointed when the picture returns from the lab. The difficulty here is similar - there’s a wide range of brightness between the foreground (the ocean, beach, etc) and the sunlit sky. So you can either take two photos - one exposed for the sky and one for the ground - and glue them together digitally or you can put a graduated neutral density filter over your lens. A graduated ND filter is darkened at one side and clear at the other so you can darken the sky and still expose for the ground. Such filters obviously take a little experience to use effectively, however.

I need help! I’m shooting a wedding this weekend. What film and lens should I use?

Okay. The usual response to this type of question is as follows: if you’re asking such basic questions then you shouldn’t be taking photos of a wedding if you’re supposed to be the photographer of record. Find a professional right now.

If you’re just going to the wedding as a guest and you want to take some snapshots, and the wedding party are relying on someone else for the main photos, then sure. Grab some low-contrast professional film like Fuji NPH/NPZ or Kodak Portra NC, a fast zoom lens and a flash with a diffuser or flash bracket, and have fun.

Why is this the usual response? Isn’t it kind of elitist? Well, people tend to place a massive amount of emotional importance upon their wedding pictures. A given wedding is a one-off event. You can’t go and get everybody back in the church or synagogue or temple or garden and do some retakes if you screw up. People expect a certain level of production value from other people’s wedding pictures (which are often taken with medium format cameras for extra image quality, not 35mm cameras) and will likely be rather disappointed by ho-hum pictures. And a sure-fire way to damage a friendship or family relationship is to mess up someone’s wedding photos badly.

Of course, hiring a professional is by no means a guarantee of anything. There are tons of lousy pro wedding photographers out there who are incompetent or who overcharge or whatever. But at the very least if someone else does the photography you aren’t risking your friendship or relationship.

Now, having said all this, that’s the usual advice. And you don’t have to follow it by any means. I didn’t and managed to pull off some okay (but sadly not brilliant) wedding shots as an amateur. It was a combination of doing a lot of testing at the venue beforehand with different film and flash settings (and careful note-taking), renting professional-quality gear, and blind luck. And I did it because the wedding party in question couldn’t afford even the lousiest pro photographer. But boy, was it stressful! I also took the photos at my own wedding, but that’s another story altogether. (yes, I’m still married)

Is it true that taking a person’s photograph steals their soul?

Yes. This is why movie stars, fashion models, politicians and pop singers have such dreadful personality and relationship problems - their souls have been severely depleted by all the photographs which have been taken of them.

Film.

What is film grain?

A photograph may appear to be made up of smooth continuous tones but close examination of film or paper with a magnifying glass or microscope reveals a different story. The images on film and paper are recorded as tiny microscopic dots, dots scattered in a diffuse pattern across the emulsion surface. The larger the dot the darker it is, so many large dots indicates a dark area and smaller dots a light area. Unlike computer graphic pixels, film grain is not in a regular linear grid.

A picture with pronounced grain at normal viewing distance is very grainy. Highly obvious grain can be caused by processing problems, or can be simply an inherent property of the film. Generally speaking, slow film (film which does not react rapidly to light) has finer grain than fast film (film which reacts rapidly to light) - see the section below on film speed. Enlarging a picture will also enlarge the grain. Sometimes visible film grain is considered an undesirable thing, and photographers go to great lengths to use slow film to minimize its appearance. Other times photographers may deliberately use fast film and certain chemical processes in order to enhance visible grain. It all depends on the type of look you’re trying to achieve.

What is film speed (ISO)?

Film reacts at different speeds when exposed to light. “Slow” film takes a relatively long time to respond to light and so requires longer exposure times or wider lens apertures or both. “Fast” film is more sensitive - it reacts relatively quickly and so requires less light. Film speed is thus a measure of film sensitivity.

Film speed is rated according to standards maintained by the International Organisation for Standardisation, confusingly known as ISO (not IOS). (old-timers may recall older film speed standards, such as ASA and DIN) These film speeds run from small numbers to large, with small numbers indicating slow film and large numbers indicating fast film. Here is a list of common film speeds, with boldface speeds being the most common.

64   100   160   200   400   640   800   1600

The advantages of fast film are obvious. You can use them at lower light levels without flash, you can get faster shutter speeds, particularly with longer telephoto lenses, and so on. So why use slower film at all?

Well the primary reason is quality. Slower film typically has smaller and finer grain size (see previous question). Faster film is faster in large part because the silver halide grains are physically much larger. Unfortunately this mean that faster film is also more obviously grainy than slow. Technological advances over the past few decades mean that fast film available today usually has much finer grain than film of the past, but it’s still the case that, all other things being equal, slower films have a quality edge.

Digital EOS cameras have adjustable light sensitivity that’s calibrated to mimic the traditional ISO scale. Interestingly enough, digital cameras have similar issues to film when it comes to light sensitivity. Generally speaking, the faster the ISO setting on a digital camera the more digital noise you get in the final photo.

What do film codes like EI 100/21° mean?

These codes refer to the film speed of the film. EI stands for “exposure index,” the first number is the old American ASA or modern international ISO film speed, and the second number is the German DIN film speed. Confusingly, the degree symbol refers to the DIN film speed and not to temperature.

So in this case EI 100/21° refers to what everybody calls ISO 100 film.

Note that this explanation is a vast oversimplification of the ISO film speed system, which has a complex backstory owing to political and technical reasons. It’s just easiest to think of EI 100/21° as ISO 100, since that’s the film speed labelling system that all modern cameras use these days.

What are C-41 and E-6?

C-41 is the code assigned to the most common colour print film processing system used for 35mm film today. E-6 is the code assigned to the most common slide (reversal) film processing system used today, developed for Kodak’s Ektachrome product line.

While both processes were originally developed by Kodak, most other film manufacturers support the same C-41 and E-6 processes. That is to say, each manufacturer’s product has a different chemical composition and colour/contrast attributes, but nonetheless the same chemical processing systems can be used on all compatible films.

What is DX?

DX coding is how modern 35mm cameras know automatically what film speed setting to use for each roll of film. Before the introduction of DX coding in the 1980s you had to set the film speed for each roll yourself, and it was easy to forget to change the camera setting when loading film.

DX is a loose acronym for “data eXchange,” and refers to the series of black and silver squares on the side of most 35mm film canisters. These squares are a code, readable by most 35mm cameras including all EOS cameras, which tell the camera what film speed to use. The camera body contains a series of gold or silver pins in the film cavity which reads the code via simple electrical conductivity. (ie: black paint does not conduct electricity and bare metal does)

All EOS film cameras have manual ISO controls so you can override the automatic DX film speed setting if you prefer. These manual controls can also be used to set the film speed for those few film canisters which lack DX codes. Infrared film and handloaded film in plastic canisters, for example, usually lack DX coding.

What is film latitude?

Latitude refers to the exposure tolerance of a photosensitive material.

Narrow latitude film, such as slide film and infrared film, has a very narrow range - your exposure has to be pretty well spot on for the image to be exposed accurately. Colour print film, by contrast, has very wide or forgiving latitude, which means that exposure requirements are somewhat less rigorous - you should still be able to get a printable picture from the negative even if the camera was set a stop or two out from the desired exposure setting.

What is infrared film?

Ordinary film is capable of recording the visible light spectrum. However, there’s a lot of energy (specifically, electromagnetic radiation) out there at other wavelengths which our eyes cannot see. Ultraviolet (UV) and infrared (IR) energy are both forms of energy that are invisible to us.

Infrared film is thus film capable of recording a portion of the infrared spectrum. There are different types of IR film with different technical specifications - some can see further into the infrared spectrum than others. The most commonly used types of infrared film include Kodak HIE, Konica 750 and Ilford SFX (all black and white print) and Kodak EIR (colour slide).

Note that, contrary to popular misconception, infrared film is not really capable of detecting heat. Infrared photography is not the same thing as thermal imaging. Heat energy involves a different part of the spectrum - a section to which IR film is not sensitive. So you can’t put IR film into your camera and see heat-loss patterns on a house or see someone’s body underneath their clothes or anything exciting like that. Sorry. For more information on this and other popular myths please have a look at my Infrared Myths article.

IR photography does, however, let you see the world in strange and unusual ways. Deciduous leaves, for example, reflect a lot of IR energy and so glow a beautiful white on black and white IR film. Clear (non-cloudy or non-hazy) skies are jet black. Colour infrared film results in strange and bizarre colour shifts. There’s a surreal quality to IR photography that many people find very intriguing.

Unfortunately most Canon EOS film cameras contain small internal light-emitting diodes (LEDs) which produce IR energy. These LEDs are used for counting film sprockets as part of the motordrive mechanism, but have the unfortunate side-effect of fogging the edge of high-speed (Kodak HIE and Kodak EIR) infrared film. For more information on this problem have a look at my EOS and IR article.

Note that most digital cameras can also be used for infrared photography if light-blocking and infrared-passing filters are installed. However, nearly all digital cameras sold today, including the current Canon EOS lineup, include infrared-blocking filters as part of the image sensor assembly to keep reddish IR fringing to a minimum. This means that they can be used for IR photography, but only with inconveniently long shutter speeds. The cameras can, of course, be modified but at the cost of lowered quality for regular light photography.

I have some expired film. Can I use it?

Film, like milk, doesn’t instantly drop dead the moment the expiry date arrives. Especially if the film has been stored in low temperature, low humidity environments.

There’s no harm at all in using older film, assuming it’s not decades old, say. Even if the film has an ancient expiry date you’ll probably just notice more grain and worse contrast than usual.

Should I buy professional film?

Depends on your photographic priorities and goals. If you’re taking snapshots of friends in restaurants, using inexpensive lenses and on-camera flash and developing the prints in a drugstore minilab, you probably won’t notice much difference. But if you’re going for more composed photos using slightly better gear then it may well be worth it.

The most noticeable thing is that cheap consumer film of the supermarket variety has inconsistent colour and tends to be of high contrast. Film manufacturers seem to think that consumers spend most of their time taking photos of clowns and balloons and optimize their film to produce extremely vivid and bright colour. Which is fine if you are, in fact, taking pictures of clowns and balloons. But high-contrast film isn’t so great for portraiture, for example. It tends to make people with lighter coloured skin rather ruddy looking in the cheeks, etc. Cheap film also tends to sit around in shops for long periods, often in warm locations, and that all accelerates film ageing.

For that reason it may well be worth it to pick up some decent pro film. Fuji’s NP series (NPS - ISO 160, NPH - ISO 400 and NPZ - ISO 800) is popular colour print film, as is Kodak’s Portra series. Both lines are popular with wedding photographers because their lower contrast and smooth tonality make taking wedding photos (often with high contrast blacks and whites) easier. If you want higher contrast but pro-level sharpness, Fuji’s Velvia slide film is popular with many nature photographers.

Professional film, especially when bought in bulk, doesn’t really cost that much more per roll than cheap drugstore film. And it costs just as much to develop a roll of crummy film as it does good film. So why not spend the small percentage extra and go for good film?

Why do photo shops store some film in refrigerators?

All film exhibits slight colour shifting as it ages. It also gets grainier as it gets old. These changes are not acceptable for professional photographers, particularly those in commercial photography who require absolutely dependable colour stability.

Professional film is thus stored at cool temperatures in order to slow the ageing process. By contrast, consumer film is shipped out pre-aged and generally sits around in shops for who knows how long, and so its colour rendition is considerably less reliable.

Is it true that film contains animal gelatine?

Yes. It appears that all film manufactured commercially today contains silver halide crystals suspended in a gelatine emulsion, which is animal-derived protein - boiled animal bones and hides. I believe all major film manufacturers use animal gelatine, but please email me if you know of any which don’t. This is obviously a problem for people who, for ethical, religious or philosophical reasons, want to avoid animal-based products.

If you find this a matter of concern you might want to consider digital photography. Digital cameras and printers have obvious environmental issues surrounding their production and eventual disposal, but animal gelatine is not, to the best of my knowledge, used.

What is “chromogenic” black and white film and why can it be developed in colour photo labs?

Traditional black and white film was usually silver-based for most of the 20th century. To be more accurate, silver halides were and are used to record and show images. Other metals were used as well, but silver became dominant.

Colour film uses silver to record the image as well, but the silver is typically washed out of the film during processing and colour dyes used to store the final colour image. Standard colour print film, known as C-41, uses a complex chemical process with “chromogenic” dyes. (the word chromogenic comes from the way the colour dyes are generated in the film during processing) And of course someone realized one day that instead of using these chromogenic dyes to record colour information you could use a simplified chromogenic process to record black and white information.

So that’s what chromogenic film is - black and white film which uses chromogenic black dye rather than silver. The advantage is that you can take chromogenic film to any minilab or wherever and have them process your black and white photos using standard colour chemistry. Minilabs cannot process traditional silver halide black and white film using their automated colour processing machines because of the incompatible chemical processes.

Printing and processing.

I got an enlargement made and tons of stuff is missing off the edges!

There are two possible issues here. First, labs tend to crop off a small amount on all sides when making enlargements. That’s how the printing machines work. The amount trimmed off is fairly minimal, however.

Second, you may be having an issue with differing aspect ratios. The ratio of the tall to wide dimensions in regular 35mm film is exactly 2:3. Unfortunately a lot of popular print and picture frame sizes do not have this aspect ratio for random historical reasons. If your photo is missing stuff from the sides but not the top and bottom then you probably have an aspect ratio issue.

For example, in North America 8"x10" is a popular picture frame size. And 8"x10" obviously doesn’t have an aspect ratio of 2:3. If you want an enlargement containing all the stuff that’s on the negative you’ll have to choose an enlargement size that can accommodate this. In the example above 8"x12" is probably your best bet. Alternatively you could ask for the image not to be cropped, but a non-cropped 8x10" photo will have white strips along the top and bottom edges to make it fit, much like a movie on TV is letterboxed.

My pictures all look lousy! Why?

This is such a general question that it’s hard to know where to start. There are so many possible reasons why a photo could look bad. Maybe there’s a problem with the camera’s focus or metering. Maybe it’s a poor lens. Maybe the lens or camera are out of alignment. Maybe your technique is bad - too much camera shake, perhaps. Maybe your composition is bad. Maybe you focussed on the wrong thing. Maybe you need to learn about lighting and using it effectively. Maybe you used onboard flash, which tends to make things look flat. Maybe you took the film to a lousy lab. And on and on.

The first thing I would do if your photos look sort of bad is to see if it’s the lab. The lab is the final link in the chain that determines the quality of your photos, especially if you’re making prints. A lab with badly maintained printing machines operated by poorly-trained monkeys, like the typical drugstore, will produce really crappy prints.

The standard recommendation, therefore, is to try shooting a roll of slide film. When you look at the slide you’re looking at the first generation image up there on the wall. There’s no lab between you and your film messing things up. If your slides look poor then it’s time to look into other possibilities.

My pictures look grainy. Why?

If you have noticeable grain or speckles on your film-derived prints it’s very probable that your negatives are highly underexposed (ie: they were not exposed to sufficient light). When photo printing machines encounter underexposed negatives they tend to boost the brightness to compensate, which tends to reveal bad speckly grain. Take a look at your negatives by holding them up to the light. If they seem very transparent and light then they’re underexposed. There isn’t much you can do about the existing negatives but it suggests that perhaps you need to meter more carefully - or apply some exposure compensation - in the future.

If you shot digitally then you may have used a high ISO setting. This is particularly the case with older EOS digital cameras. ISO 100 is pretty well noiseless, but the higher you go with your ISO settings for low-light photography the more random rough-textured "noise" appears on the image.

There are other possibilities. It’s possible that you had the ISO film setting on the camera wrong, for example. It’s also possible that the lab messed up the development of the film.

What is colour temperature?

The definition of colour temperature is highly technical - it refers to the colour of light produced by a theoretical “black body” object that’s heated to a certain temperature, measured in Kelvin temperature units.

Though based on physical theory there’s nothing abstract about this. The concept is crucial for colour photography. Essentially it boils down to the fact that white is not an absolute concept.

White light produced by a light source with a low colour temperature such as a tungsten light bulb is very orange compared to the bluish white light produced by a light source with a high colour temperature , such as the sun. This isn’t really apparent to the human eye under normal circumstances because our brains adjust automatically to changing colour conditions. It’s only usually noticeable when light sources with different colour temperatures are seen together. For example, the incandescent light spilling out of the window of a house looks remarkably yellow or orange at dusk, when everything outside is lit with the very blue light from the darkening sky.

Unfortunately, film is not so flexible. Film emulsion must be designed from the start to assume a certain colour temperature as its white point. Most films are daylight-balanced, which means they assume that the light from the noonday sun (in a temperate place) is white - roughly 5500K. So if you take a photo indoors under tungsten lighting using daylight film you’ll find everything looks very orange or yellow. You can also buy film that’s balanced to tungsten light - typically 3200K. If you take a photo outdoors using such film you’ll end up with a picture with a very blue cast.

Digital cameras generally do not have a problem with colour temperature in the same way. Since digital data can easily be reconfigured it’s a simple task to alter the white point of a digital camera - a process called white balance. Most digital cameras and all EOS digital cameras have preset white balance settings for common light sources - daylight, tungsten light bulbs, shade, etc. EOS digital cameras also let you set your own custom white balance. However, if you forget to set the white balance correctly when taking a photo you might end up with similar problems to film colour casts, assuming your camera wasn’t using automatic white balance.

My pictures have strange colour tints. Why?

The most obvious possibility is, of course, a problem at the lab. This shouldn’t be a problem with labs that demonstrate a modicum of care, but strange things happen. Once I took a test roll of film into a local corner one hour photo lab and got back a stack of pictures of my green fiancée. Green. Really. It was like “I Married a Martian.” I took the same negatives to another lab and came back with a stack of nicely coloured pictures - Martian princess no more.

The most likely possibility after that is colour temperature issues. Here are some common scenarios, expanding on the colour temperature section above:

Photos, particularly indoor photos, have a yellow-orange tinge to them.
You probably used daylight-balanced film under tungsten (incandescent) lighting. Tungsten light records as yellow-orange on daylight film.
To avoid this problem either use tungsten-balanced film, use flash, turn off tungsten lights and rely on daylight coming in through windows, or put cooling (blue-tinted) filters on your lens.

Foreground stuff looks fine but background stuff is tinged yellow-orange.
You probably used flash under tungsten lights with daylight-balanced film. The light from flash units is designed to be the same approximate colour temperature as sunlight. So all foreground objects illuminated by flash will appear normally coloured on daylight film.
There’s no real way to avoid this problem if you’re shooting with flash. You could either not use flash or turn off any tungsten lighting. Or you could use tungsten-balanced film and put a warming filter on the flash head.

Photos, particularly outdoor photos, have a blue tinge to them.
Less common, but you may have used tungsten-balanced film under sunlit conditions. Regular daylight records as blue to tungsten-balanced film. Switch to daylight film or put a warming (yellow) filter on your lens.

Indoor photos look greenish.
Most likely the pictures were taken under fluorescent lights. There’s no such thing as fluorescent-balanced film, but you can buy magenta-tinted filters (FL filters typically) which can help colour-correct fluorescent light. Note that many modern fluorescent bulbs don’t have this same problem.

Which is better? Matte or glossy?

Neither. The choice of matte or glossy print surfaces is a matter of personal preference.

Some people prefer matte because it’s less reflective - so there’s less glare - and because fingerprints tend to show up better on glossy surfaces. Other people prefer glossy since the lack of texture can make the image look a bit sharper. Many others prefer pearl or semi-matte surfaces as a compromise between the two.

What is cross processing?

Cross processing refers to developing a film using a development process that was not intended for it. It usually means developing slide film using a print developing process or vice-versa.

Cross processing is sometimes done because it yields interesting, albeit unpredictable effects. Contrast tends to be enhanced and colours tend to shift. Edgier fashion and commercial photography is sometimes done using cross processing. Note that many labs won’t do cross processing, sometimes because their automated machines refuse to let them do it, sometimes because they’re concerned about their photochemicals getting contaminated and sometimes because they have no idea what it is.

What does “archival” mean?

The ravages of time are cruel, though more cruel to some materials than others. Archival media is paper, film, etc, which is supposed to hold up reasonably well to the passage of time. How well it does is dependent on a host of factors, and there’s no universal definition as to what is truly archival quality material and what is not.

Paper.
Paper is probably the main area of concern when it comes to archival materials. Standard commercial papermaking processes result in paper with a high percentage of acidic materials. And unfortunately this acid causes paper yellowing and deterioration (crumbling) - sometimes in months, often in years and always in decades. For that reason archival papers must be “acid-free,” or have a neutral or slightly basic pH. Papers are also often “buffered,” which involves the addition of an alkaline material such as calcium carbonate to help ensure long-term pH neutrality.

Another problem with papers made from wood pulp (as opposed to higher quality papers made from cotton) is the presence of lignin. Lignin is a naturally occurring part of a plant cell, but is an undesirable substance in paper as it can contribute to the long-term deterioration of the material. Higher-quality paper has had most of the wood fibre’s lignin removed during manufacture.

Binders.
Photo binders must also be designed with archival properties in mind to avoid damaging photographs. Many photo binders use thin plastic sheets to keep photos in position. Mylar sheets appear to be pretty stable, but cheap products may use lesser quality plastics which actually stick to the photos, ruining them. The pages of the binders must also be made of acid-free paper if they come in contact with the photographs, or else you’re defeating the purpose of using acid-free paper in the first place.

Colour dyes in film.
Dyes are another area of concern when it comes to archiving photographs. Traditional silver-based black and white processes are generally remarkably stable - a black and white picture taken a century ago can look just as good today. Colour dyes, however, are notoriously difficult to keep stable. Colour dyes used in motion picture film in the 60s and 70s, for example, are fading at an alarming rate.

The same problem applies to the colour dyes used in many forms of colour still film. Some colour film technologies, notably Kodachrome, have proved to be very stable in dark storage, but typical cheap colour print film (chromogenic film) doesn’t have particularly good archival properties. It might be worth doing high-resolution scans of important photographs now, before the colour has deteriorated at all. You then have the problem of preserving the digital data (see below) but at least the colour in the digital scans won’t fade.

Computer prints.
Dyes used by inkjet computer printers have similar problems with colour fading. Some early inkjets, in fact, were notorious for severe colour fading and colour shifting problems, particularly when exposed to ultraviolet light. Many inkjet makers indicate that their products are “colourfast” or “archival,” but these claims don’t follow any particular standards.

Computer data.
Computer data itself is a complex problem as well. Binary data itself can be duplicated over and over completely error-free, but the media upon which the data is stored is subject to failure over time. Floppy diskettes, for example, suffer from what’s jokingly called “bitrot” - they lose their magnetically-encoded information over time. Hard drives pack a huge amount of data into a tiny area on disc, and it’s unclear how long they can retain their data.

Recordable CDs (CD-Rs) are a technology heavily relied upon for archiving digital data. Accelerated tests performed on the cyanine (typically green or blue-green), metal-stabilized cyanine (also typically green or blue-green), phthalocyanine (typically gold or greenish gold) and metallized azo (typically dark blue) dyes used in different types of CD-Rs suggest that CD-Rs will enjoy many decades - perhaps even a century’s worth - of reliability, but only time will tell how stable they really are.

Not only are the dyes a factor but the stability of the polycarbonate plastics, the environmental storage conditions (eg: abrasion, water vapour, airborne pollutants such as sulphur, and shock can all degrade CDs), the chemicals used in any adhesive labels or felt-tip markers, and the burn power of the CD burner itself are all elements which will determine how long the discs remain readable. Not only that but 550 MB/63 minute CDs, which use a slightly wider track spacing than 650 MB/74 minute CDs, are often more reliable in many older burners and readers.

And of course who knows whether the actual equipment to retrieve data from a given medium will be around in decades or centuries hence. How many people today have the gear required to retrieve data from a computer cassette recorded in 1977, for example? Or a Bernoulli cartridge from the 80s? Will it be easy to copy that precious digital photograph from a CD in 2050? Will anybody be able to retrieve data from a corrupted flash memory card in a century’s time? From this point of a view a photographic negative may well have longer longevity.

What to do?
Well, it’s basically impossible not to have some colour or data loss over the years, but there are a few things you can do to help minimize the problem.

Digital.

Why are Canon EOS digital cameras so expensive?

Very simply, it’s because it costs more to build a digital camera than a film camera given today’s technology. Technology is, however, changing at an incredible rate, and it’s just a matter of time before the two technologies are reversed when it comes to cost, just as CDs once cost considerably more than vinyl records.

Canon have produced a number of digital cameras compatible with the EOS system over the years. The first generation of these cameras was built in conjunction with Kodak. They were modified Canon EOS film camera bodies (the top of the line 1N) with film transport components taken out and Kodak-designed digital equipment stuffed inside the body and its add-on grip. This DCS series of cameras - the DCS3, DCS1, D2000 and D6000 - was mainly aimed at professional photographers who needed to be able to send photographs from the field rapidly and were at the cutting edge of digital photography at the time. They were thus very expensive - the 1.3 megapixel DCS3, for example, listed at over $15,000 US when it came out. Today you get better resolution than that (though not better lenses, admittedly) in ordinary mobile phones.

The second generation of Canon’s EOS digital cameras were and are wholly built and designed by Canon and are digital cameras from the ground up - they aren’t retrofitted film bodies like their predecessors. Unlike digital point and shoots the D30, D60, 1D, 1Ds, 10D and so on are all fully compatible with the EOS line of lenses and accessories and offer excellent image quality. But they too are considerably more expensive than point and shoot digital cameras.

Why is this? Well, there are many reasons involving R&D costs, high market demand and so on, but a significant factor is the cost of making large digital image sensors. Point and shoot digital cameras all have really tiny image sensors which are quite cheap to produce. Digital EOS cameras, by comparison, use much larger image sensors, from the full-sized 24x36mm sensor of the EOS 1Ds and 1Ds mark II to the smaller APS-sized sensors used in the other cameras.

Still, prices are falling rapidly and used digital cameras can be had today for a fraction of what they cost new. The cheapest Canon digital EOS camera is a few times the price of a cheap film camera, but you can make that back in film processing costs very quickly. Digital EOS cameras are nearly as affordable as midrange film cameras, though it’ll probably be a while before they’re as cheap as low-end film cameras.

Why doesn’t the back screen on my EOS digital camera display a live video preview?

Unlike point and shoot digital cameras, Canon EOS digital cameras are SLRs, which means they use mirrors. The image sensor is situated behind the mirror, so no light reaches the image sensor normally but is instead deflected up into the viewfinder. When a picture is taken the mirror flips up out of the way, blacking out the viewfinder and letting light reach the image sensor. Using this design means there is traditionally no way to have live image previews on the rear screen of the camera and have a working optical viewfinder at the same time, since the mirror is normally down and blocking the light path to the image sensor.

Canon (and other makers of digital SLRs) have historically designed their cameras this way since digital SLRs are meant to appeal to the same sorts of people who bought film SLRs and want their digital cameras to work the same basic way as film cameras. There are also technical reasons why live image previews are tricky with digital SLRs. A few approaches are:

As it turns out, there has been enough demand for this sort of live preview that Canon and other digital SLR makers have come up with ways of implementing it. Sony have announced a camera which uses the second technique above. Canon now sell cameras using the third technique, which they call LiveView.

The first EOS camera to support a form of LiveView was the limited edition EOS 20Da, intended for astrophotography. It flipped up the mirror and permitted a preview, but it only worked in low light levels and you couldn’t meter or autofocus when the mirror’s up, so it wasn’tin the least bit useful for the casual photographer. The next cameras to support LiveView did so in a more useful fashion. The 40D and 1D mark III allow live previewing with the mirror up. However, autofocus is not available.

Why are the pictures from my digital camera soft-looking?

Digital EOS cameras assume you’re going to be applying sharpening filters to the images once they arrive on your personal computer. In other words they don’t do much by the way of sharpening inside the camera so as to give you lots of control over the image.

So all you need to do is to apply a little sharpening (eg: “unsharp mask”) to your pictures and they should look quite sharp and crisp.

What are RAW and DNG and why is there a controversy about them?

Film cameras output information in a fairly accessible and universal format. You have a transparent piece of film negative and that’s it. You can store the negative and retrieve the image any time you like using standard equipment.

Digital photography is very different, since images are captured using computers and stored as computer files. The problem is - what format should be used for the file? Just as word processing documents can be stored in a variety of different and incompatible formats, (plain text, RTF, Microsoft Word, Wordperfect, Wordstar, HTML, etc, etc) digital pictures have to be stored in a file format.

JPEG is the most common format used for storing digital pictures. It’s an open standard, meaning no one company has total control over it, and it efficiently compresses files to keep them small. (strictly speaking JPEG - the for Joint Photographic Experts Group - refers to the compression method and JFIF - JPEG File Interchange Format - the file format, but that’s getting obscurely technical, since everybody lazily refers to the files as JPEG files)

The problem with JPEG is that it does not store all the information gathered by the camera. It compresses the image in a lossy fashion, which means it discards picture information that people are unlikely to notice. That’s great for minimizing storage requirements, but the drawback is that a serious photographer isn’t going to be very keen on losing picture quality even to save space.

So most decent digital cameras also store pictures in RAW format or something similar. RAW isn’t an acronym, but simply refers to the raw, largely unmodified data sent straight from the camera’s image sensor. This is often referred to as a “digital negative” since it’s the most basic and primal way that digital picture information can be stored.

The problem with RAW is that it isn’t a universally defined format of any kind the way JPEG is. Each camera outputs picture data in its own unique way. Camera manufacturers have generally not been interested in adopting any form of common standard - in fact, RAW image formats frequently vary from model to model from the same manufacturer! You then need to use the software supplied by the camera maker to transform the RAW image data into a more universally useful format, such as JPEG or TIFF.

Unfortunately most proprietary software made by camera makers has tended to be sluggish and inefficient to use, particularly in a professional context. So third party applications have stepped in to provide more useful file conversion utilities to the digital photography market. Adobe’s Camera RAW, Phase One’s Capture One and Bibble are the most common third-party RAW processing programs. Having such programs works well, though of course it does represent an added expense to digital photographers.

The controversy here is twofold. First, as noted, camera makers keep releasing new cameras with new RAW formats, and the makers of third party programs keep having to update their applications. For example, Canon have variously used CRW, TIF (though customized) and .CR2 files; all of which are incompatible with each other and require updated image viewer and converter programs. This lack of openness is troubling. What happens if you decide to take a look at some of your photographs in 20 years and find that there is no longer any image processing software for it? All of a sudden your pictures are gone and useless. Meanwhile you can still take that shoebox off the shelf and rescan your film negatives all you like.

And second, and even more problematic, at least one camera maker has taken steps to block access to their internal file format. In 2005 Nikon introduced the D2X digital camera, which brought with it encrypted white balance data. What this means is that Nikon deliberately lock away white balance information for no reason other than to prevent other applications from opening the files. This is a step beyond the usual practice of camera makers arbitrarily altering lookup matrices for colour and white balance data and so on from camera model to camera model.

From a technical perspective there’s nothing to prevent someone else from cracking the encryption and providing software to open these files. But legislation in a number of countries - most notably the Digital Millennium Copyright Act in the United States - may make it illegal to do so. So most third party RAW readers don’t have the ability to open these files because their developers don’t want to be held legally liable for a violation of the DMCA. Therefore laws which were designed to shield large Hollywood studios and record labels from losses incurred by movie and music piracy are also preventing individuals from legitimately using the files that they legally own.

Adobe have created a fairly open standard for storing digital camera data, DNG (digital negative) which addresses some of these concerns, though it does permit manufacturers to store proprietary data and so does not entirely eliminate the concerns of many photographers. Unfortunately DNG has yet to gain much support from the major camera manufacturers. Hasselblad and Leica are the only camera makers thus far to give their support to the format. The groundwork has been set, however, in that most major image viewing applications now support DNG.

A group of photographers and interested users have formed a group, OpenRAW, to promote open standards for digital RAW files. If you’re interested in this issue you should probably take a look at their Web site.

Can my digital camera shoot black and white or multiple-exposure images?

Not all digital EOS cameras are capable of these effects in-camera. This is because users of digital EOS cameras typically use a personal computer for post processing, and apply the necessary filters and effects after capturing to achieve such effects on the computer, not in the camera. However, EOS digital cameras introduced after the EOS 350D/Digital Rebel X/Kiss N Digital do have the ability to apply simulated colour filters to capture a black and white image. Canon have not, however, seen any reason to build multiple exposure capability into EOS cameras.

If you haven’t got one of these cameras, both of these effects are easily accomplished with image editing software. In fact, many image cataloguing programs include the ability to convert an image to black and white at the touch of a button. And you have far greater control and flexibility over a multiple exposure image in Photoshop than you do in-camera.

Desaturated colour digital photos don’t look quite the same as black and white film-based photos. Why not?

Black and white film is not equally sensitive to all colours across the spectrum. Different films have different spectral sensitivities (ie: respond more to some colours than others), and experienced black and white photographers are very familiar with the tonal qualities of such films and papers.

For that reason taking a colour picture and removing all the colour information (ie: desaturating it) will not yield exactly the same results as using actual photographic film and paper. The differences are subtle but noticeable to the experienced eye. You can, however, simulate the effect of using traditional black and white film by desaturating colour channels independently in Photoshop or some other image editing program. There are also third-party plugin modules offered by various small software developers which can achieve this effect as well. And, as noted above, the EOS 350D/Digital Rebel X/Kiss N Digital can also apply colour filters algorithmically to achieve traditional black and white effects.

What is aliasing and anti-aliasing?

Digital images are made by displaying tiny dots on a (usually) rectilinear grid. Straight lines which go in either horizontal or vertical directions on this grid will always look fine, but diagonal lines can be a problem. Since such lines essentially cut across the grid pattern they can appear as rough jagged stair-step lines rather than smooth diagonal lines.

There are three common ways of reducing this effect. First, if the resolution of the image is high enough (ie: each individual pixel is small enough) then the aliasing will not be readily apparent to the human eye. Second, the jagged lines can be smoothed out by filling in the stairsteps with intermediate (eg: grey rather than black and white) values. Computer software that performs this function is commonly known as an “anti-aliasing algorithm”. Third, most digital cameras contain optical filters situated between the lens and the image sensor which smooth out the jaggies optically before it’s recorded by the sensor. Such “anti-aliasing filters” soften the image somewhat, so you lose a little sharpness, but the reduced aliasing is generally considered to be worth it.

What does “interpolated resolution” mean?

It’s a fancy way of saying “faking it.” Let’s say a scanner is capable of scanning 300 pixels per linear inch. Wouldn’t it be great if you could say it’s capable of producing 1200 interpolated pixels per inch? Well, that’s what scanner makers do! They take the 300 ppi data, quadruple it and then mathematically smooth it all out. No information is added to the original scan, but the image can (depending on the sophistication of the software algorithms used) look much better nonetheless since jagged aliasing lines can often be minimized.

Does it look as good as a true 1200 ppi scan? Nope. Could you take your 300 ppi scan and enlarge it in Photoshop using Photoshop’s bicubic interpolation software and get pretty well the same results? Yep.

What is a “digital” lens?

That depends on what is meant by “digital.” There are three main ways in which the term “digital” is applied to lenses.

1) The most common use by far is stupid marketing. “Digital” is one of those words, like “professional,” “next-generation,” “natural,” “multimedia,” “advanced,” and so on, which may have a pretty specific meaning in some ways but which is tagged onto a wide range of disparate products just to make them sound desirable. I mean, what’s particularly “digital” about a tripod? A camera bag? The word has been stripped of any real meaning in these cases. It’s a hollow buzzword of the day.

2) Second, and more meaningfully, the lens could have a focal range that’s useful for digital cameras with subframe (ie: smaller than equivalent film) sensors. For example, a lens with a focal length range of 24-85mm, when used on a subframe sensor digital camera, might have roughly the same field of view as a 38-135mm lens on a 35mm film camera. In this case the camera marketers might want to emphasize the usefulness of the lens for subframe cameras by dubbing it “digital.”

3) Third, the lens might genuinely possess optical characteristics intended for use with the current generation of digital cameras. The most common way in which it could be thus designed would be to have a reduced image circle since most digital cameras have small sensors that don’t benefit from larger image circles. The EF-S lenses are an example of this. Some lenses also attempt to produce more collimated light. Film is fairly responsive to light hitting its surface even off the perpendicular (as is often the case with wide angle lenses towards the edges of the frame). Digital image sensors, however, don’t fare as well - they work best when the light striking the sensor is precisely perpendicular to the image plane. Imagine the sensor being placed at the bottom of a shallow well - light is more likely to strike the sensor and not the well walls if the beam is perpendicular. So a lens which tries to keep light striking the image sensor in a fairly perpendicular orientation across the whole image area may indeed be better suited to a digital camera than a regular lens. Assuming, of course, that the optical gymnastics required to collimate the light don’t degrade other aspects of the lens performance.

So. In the first case the term is meaningless marketing nonsense. In the second case the lens is just a regular lens that might offer certain advantages when used with digital cameras. And in the third case there are genuine reasons why the lens might be particularly suited or (in the case of lenses with reduced image circles) only compatible with certain digital cameras.

At present Canon are not marketing any of their current lenses as “digital” products - even the EF-S lenses - though some third parties are. Canon do claim, however, that some of their newer lenses have optical coatings optimized for digital lenses, whatever that means.

What is “Err 99” on my digital EOS camera?

This error condition is analogous to the “bC” error with film cameras. It’s most likely caused by using an incompatible lens or dirty lens contacts.

Try a different lens and see if the camera works normally. Many older Sigma lenses in particular do not work with digital EOS cameras. Try also lightly cleaning the lens and camera metal contacts - this frequently clears up the condition. Sometimes rubbing the contacts with an immaculately clean pencil eraser (rubber) can do the trick, but be extremely careful not to let any crumbs or dust fall into the lens or camera. If you have a Canon lens which generates this error and cleaning does nothing then you may need to send it back to Canon for servicing. It’s possible the lens mount needs some adjusting if the lens contacts don’t reliably touch those on the camera body.

What is front focussing and what’s this about the EOS 10D having this problem?

Ideally when you use your camera to autofocus on something the item you’re focussing on should be sharply in focus. Simple enough. But if the camera consistently and erroneously brings the plane of focus ahead of the film surface (or image sensor surface on a digital camera) then you’ve got a problem, since everything will look slightly out of focus.

Unfortunately it appears that many samples of the EOS 10D digital camera have this problem. Not all do, and many cameras which seem not to be producing sharp results are probably not being used correctly. But some do. For more information on the problem and a simple way to test for it have a look at this Photo.net article by Bob Atkins.

Why does my EOS 300D/Digital Rebel/Kiss Digital rattle when I move it?

The metal struts which hold the popup flash on this camera are sort of loosely mounted and do rattle when the camera is moved. This is normal for this model.

How can I turn off the shutter noise on my Canon digital EOS camera?

You can’t. The sound you hear is the real thing. All Canon digital EOS cameras contain moving parts which click and clack when you take a photograph. They aren’t like mobile phones and consumer cameras which play simulated shutter release noises through tiny loudspeakers so that people know when the camera has taken a photo.

There are two components which make up the characteristic sound of an SLR in operation. One is the clack of the mirror flipping up to allow light through to the surface of the film or image sensor. The other is the click of the shutter opening, to time precisely the exposure of the film or sensor.

All Canon digital EOS cameras to date contain electromechanical shutters, just like film cameras. The only digital EOS camera with a digital shutter is the EOS 1D, which uses a CCD chip and not a CMOS chip for its image sensor. However, even the 1D has a moving shutter, since it’s there in part to protect the image sensor - an important thing for a camera with a removable lens. According to Canon the 1D’s shutter is also used in bulb exposures.

What is noise?

Noise has two basic meanings in the context of photography. First, there’s the obvious meaning of sound - acoustic noise heard by the human ear - mechanical shutter clicks and so on. Second, there’s electrical noise. All digital image sensors are subject, to varying degrees, to this second type of noise. This is essentially the result of individual transistors in the sensor chip erroneously saying they can detect light when there actually isn’t any, and adding spurious dots to an image.

In communications theory, noise is any disturbance which disrupts or affects or interferes with a signal in an unwanted fashion. In other words, the devices are actually responding to unwanted electrical fluctuations in their components, in much the same way that you can hear a hiss in telephone conversations or tape recordings. (hence the term electrical “noise” - it’s a term stemming from research into audio recordings, telephony and radio) Sometimes the noise actually originates from electricity flowing through the camera’s components and is thus intrinsic and unavoidable. Other times the noise originates from external sources of interference, such as radio transmitters and other electrical devices, and can be reduced by metal shielding.

Noise appears in a digital photograph as a sort of random texture of dots. Imagine the snow on an old-style TV set and imagine that snow being superimposed over top of a picture. Unlike film grain, which can have an intriguing texture of its own, digital noise generally doesn’t look very good, and camera makers go to great lengths to minimize it. Noise in a digital camera is related to image sensor sensitivity. At a simulated ISO 100 setting most digital cameras display little if any noise, but at ISO 800 or 1600 most cameras have noticeable noise. Fortunately Canon have been quite successful in minimizing digital noise over time. Earliest EOS cameras are like any digital camera and are very noisy at high ISO settings. But the most recent models are considerably less noisy.

Can my choice of memory card affect picture quality?

No. Digital cameras use binary data. A given bit of data is either true or it is false. Memory cards either work reliably under ordinary conditions or they don’t. The only points to consider between one card and another are speed of read and write access and overall reliability of the product.

Is it true that flash memory used in memory cards wears out?

Yes. The memory cells that make up flash memory cards, used in nearly all digital cameras today, do indeed have a finite lifespan. Estimates vary from product to product, and manufacturers tend not to want to talk about it, but each cell can be erased and reused anywhere from 10,000 to a million times before internal insulators start wearing out and errors start creeping in.

Does that matter? Well, for the average user, no. Even the low estimate - 10,000 times - is quite a few rounds of photography on a card. And better memory cards contain special controllers which evenly distribute which sections of a card are used in order to minimize wear.

The finite lifespan might, however, be a factor for intensive use, particularly with older memory cards. Some card manufacturers promise replacement guarantees of 1 to 5 years, but of course getting a corrupt memory card replaced for free does little to resurrect any valuable photographs which may have been lost. Still, all things considered, flash memory seems to be a pretty reliable and stable form of data storage. This is particularly the case when you compare flash memory to its main competitor - hard disk drives - which are susceptible to shock and vibration.

A related factor is how long flash memory can retain data without power. This is particularly difficult to pin down, but I’ve heard figures of around 10 years. So if, in the distant future, your grandchildren discover a box of your old memory cards it’s possible that any data on it will be long gone. That is, of course, assuming that they could find a way of reading the cards. That will probably be as difficult as getting 126 cartridge film printed today.

There’s a small irregular black blob on all my pictures. What is it?

Dust on the sensor. Unlike film cameras, which expose a fresh chunk of clean film every time you wind the camera, digital cameras use the same glass sensors. And naturally dust on the sensor will appear in the same spot on every single photo you take.

This problem will be more apparent if you shoot at a small aperture (larger f/ number) than if you shoot wide open (smaller f/ number). So sometimes shooting at a wider aperture setting will minimize the problem.

But fundamentally you need to clean the sensor. And this becomes problematic, because the sensors are quite fragile and easily scratched. You don’t want to be sticking paintbrushes or cotton swabs or whatever in your camera and wrecking the image sensor. Pressurized air bottles (technically gas under pressure, not air) also tend to leave residue, and are best avoided.

Canon themselves recommend to use nothing more than a squeezy rubber blower brush to remove dust, but that doesn’t always do it. A lot of people recommend special sensor swabs, assembled in cleanroom situations, for cleaning the sensors. These are usually dipped in pure alcohol. But if you don’t want to risk messing around that way you’ll need to take the camera to an authorized repair shop for cleaning.

And as for the source of the dust, it’s best to try and avoid changing lenses outside when it’s windy, or in dusty situations. Try as much as possible to change lenses under circumstances which will minimize the junk building up on the sensor.

What is dark noise subtraction/long exposure noise reduction?

Dark noise subtraction is a method for reducing noise in long exposures. First, the camera takes a photograph without the shutter open for the duration of the real exposure. This gives a map, as it were, of noisy pixels. Then the camera opens the shutter and takes the actual photograph. Once the photo has been taken the camera subtracts any noise present in the dark frame. Since both frames are taken under very similar conditions within moments of each other this is a reasonably successful technique of minimizing, but not eliminating, noise.