Using manual lenses and telescopes with EOS cameras.
Copyright © 2001-2007 NK Guy
Table of Contents.
Adapter ring compatibility problems and infinity focus
Problems with Canon FD manual lenses
What is stop-down metering?
But my camera has no aperture lever!
Old and new stop-down metering styles
How to use the old stop-down metering style (display shows something other than 00)
How to use the new stop-down metering style (display shows 00)
Adapting EF lenses to non-EOS cameras
One area of interest to a lot of Canon EOS camera users involves attaching old manual lenses and telescopes to their autofocus cameras. Canon dont say anything about this in their manuals - they just include a warning about how using non-Canon lenses might somehow ruin your camera. While this may theoretically be true, in real life its not a problem. And opting for non-Canon lenses opens up all kinds of interesting choices to you.
A number of third-party manufacturers build autofocus lenses which are designed to be fully compatible with Canon EOS cameras and their EF (electrofocus) lens mount system - Tamron, Tokina and Sigma being the big three. On the whole these third-party lenses are quite compatible with EOS cameras. A number of older Sigma lenses cause newer EOS cameras to lock up temporarily, but Ive personally never heard of any third-party EF-mount lens permanently damaging a camera, though I suppose anything is possible.
But what about lenses meant for other camera mounts? Well, many such lenses can be adapted to Canon EOS cameras through the use of special adapter rings. Not all, of course. For example, a lens designed to work with a non-Canon EOS autofocus camera (eg: an autofocus Nikon, Pentax or Minolta camera) isnt going to work with an EOS camera very well since the electronics are totally incompatible. However, older fully-mechanical manual lenses can often be adapted successfully to EOS cameras. So can many telescopes and spotting scopes. Heck - so can magnifying glasses attached to EOS bodies with cardboard tubes and a lot of tape! And you can even buy all-manual lenses with EF lens mounts built in, such as the Lensbaby selective-focus lenses, and the Loreo Lens in a Cap.
Of course, certain issues arise in using these manual lenses, and thats what this document is about.
Note that this document does not deal with the four Canon-built manual-focus lenses currently in the EOS-compatible lens lineup - the three TS-E tilt-shift lenses and the MP-E 65mm 5x macro lens. Although these exotic and highly specialized lenses lack autofocus motors (and hence lack the official EF appellation since they are not "electrofocus") they nonetheless have EF lens mounts, EOS-compatible electronics and electronically-controlled aperture diaphragms.
First of all you have to buy the appropriate physical lens adapter required to get your lens attached to your camera. For this you should consult your favourite camera shop - I cant help you here. But a number of manufacturers build simple metal ring adapters that let you attach various types of lenses. Robert Monaghans page, listed at the end of this document, mentions a few retailers and manufacturers of such adapters.
If youve got, for example, a lens designed for an old Pentax threaded (screw mount) camera like the Pentax Spotmatic youll need an adapter for M42 lenses. Same with the new line of Carl Zeiss ZS lenses, which also use M42. If you have a telescope youll probably need a T-mount adapter, assuming your telescope has the ability to be hooked up to a camera at all. Or if you have a Nikon lens youll need an adapter that lets you fit Nikon F lenses to your EOS body. Likewise Leica R, Leica Visoflex, Olympus OM, Contax/Yashica RTS, Rollei, and Contax manual focus, or even big Hasselblad, Mamiya 645, Pentacon 66, Pentax 645 and Pentax 6x7 medium format lenses can all be adapted. Microscopes apparently often require C-mount adapters. Tamron built a series of Adaptall II lenses and you can still occasionally find used Adaptall II->EOS adapters around. I have links to some sources for these adapters at the end of the page.
Most adapters are simply metal rings with an EF bayonet on one side; usually worth around $20-50 US. And since the EF mounting ring is larger in diameter than most 35mm SLR lens mounts quite a few lenses can be adapted to the EOS system.
Adapter ring compatibility problems and infinity focus
The most common problem is that of lens registration - the distance from the lens mount to the film plane. It may not be possible to build a lens adapter that gets this distance right for certain lens mount systems.
For example, the back focus distance (distance from the rearmost lens element to the film plane) on EOS cameras is 44mm, but on Leica rangefinder cameras its 27.8mm. Matching the back focus distance would require a lens mounted deep inside the camera body; not usually an option. In cases such as this you may either have to buy an adapter ring that wont let you achieve infinity focus (fine for macro photography; probably not fine for anything else) or youll have to get an adapter ring which contains one or more glass lens elements and which will inevitably degrade the image quality somewhat. These compensating elements let you achieve focus to infinity, though at the expense of image quality. Contax G, Konica F, Leica M, Minolta MD and Miranda lenses are other lens mounts with back focus distances less than that of Canon EOS.
There is also the case of lenses which have lens register distances very close to that of a true Canon EF lens. Contax/Yashica lenses (45.5mm) and Canon EF lenses (44mm), for example, have only a 1.5mm difference in lens registration, and 1.5 is awfully thin for a metal ring adapter. Such adapters have to be machined to incredibly close tolerances in order for infinity focus to work, which means they can be quite expensive. Cheaper ones often have to be sanded down to maintain infinity focus - but even that is something of a dodgy proposition as you have to sand the surface down accurately from one side to the other, down to a fraction of a millimetre.
Sadly it also appears that it isnt possible to make adapter rings that let you mount Pentax K (bayonet mount) lenses on EOS cameras with EF lens mounts. The Pentax K diaphragm coupling lever physically interferes with such a possibility. So youd have to modify the lens (or the camera) to make such a conversion possible. Note that this does not apply to cameras compatible with the EF-S mount. The design of the EF-S mount, with its smaller mirror box thanks to the 1.6x crop factor, coincidentally permits the use of such lens adapters.
Finally, and this isnt strictly to do with manual focus lenses per se, but you cant use Minolta Vectis or Four Thirds (Olympus, Kodak, Fuji, Sanyo, Sigma, Panasonic and Leica) lenses on EOS cameras. These lenses, in addition to being autofocus lenses, cast very small image circles; much too small to cover the imaging area of EOS cameras. In theory I suppose the Vectis lens design might cover an EF-S sensor, but it would probably be pointlessly expensive to make such an adapter.
Problems with Canon FD manual lenses.
Canon FD lenses are manual-focus only lenses which Canon sold in the years before switching over to the autofocus EF system. Many, particularly those made in the late 70s and early 80s, offer excellent optical quality, have smoothly-operating metal barrels and are available quite inexpensively on the used market. So the obvious thought comes to mind - can such lenses be attached to EOS cameras?
Unfortunately the lens mounts used by the two systems are completely incompatible. FD lens mounts are smaller in diameter, have a different lens register from EF lenses, rely on mechanical levers to control lens aperture, are of a breech-lock design (rotating pressure ring) and never contain autofocus motors.* EF lens mounts are larger in diameter, are of a bayonet mount design (put lens into camera and rotate partway to lock), support electronic control of the lens aperture and the lenses usually contain autofocus motors.
So. When it comes to adapting FD lenses to EOS cameras the key difference here is the lens register incompatibility. Adapters for Canon FD-mount lenses, including the two adapter models that Canon themselves sold at one point, must deal with this incompatibility somehow. Either they contain optics (glass lens elements) to compensate for the register difference and retain infinity focus or else they dont contain optics and dont retain infinity focus. Theres no way around this.
Canons optic-containing FD-lens-on-EOS-body adapters were basically small teleconverters (1.26x) and only worked properly with a number of their longer telephoto lenses - effectively transforming them into longer slower lenses - you lost 2/3 stop. The full official list of compatible lenses is:
FD 200mm 1.8 L
FD 200mm 2.8 RF
FD 300mm 2.8 L
FD 300mm 4
FD 300mm 4 L
FD 400mm 2.8 L
FD 400mm 4.5
FD 500mm 4.5 L
FD 600mm 4.5
FD 800mm 5.6 L
FD 50-300mm 4.5 L
FD 85-300mm 4.5
FD 150-600mm 5.6 L
The adapters cant be used on other lenses because they have large protruding front elements which physically interfere (collide) with the rear lens element on other FD lenses. They were known as the Canon Lens Converter FD-EOS and were not sold to the public - only accredited professional photographers could acquire them through Canon Professional Services. Apparently they were intended to help pro photographers who had a big investment in huge Canon FD telephoto lenses make the transition to the EOS system. These adapters are thus quite rare, specialized and hard to find today. When they appear on auction sites they tend to have rather high winning bids.
Third parties have made similar glass-containing adapters, but by contrast their optics are usually poor and thus image quality tends to be generally low.
Canon and others also made FD lens to EOS body adapters which do not contain optics, but as noted above, you lose infinity focus and so such simple metal ring adapters are really only useful for closeup applications. In fact, the Canon model (which was sold to the general public) was marketed under the name Macro Lens Mount Converter FD-EOS. Theres also a more subtle metering isue with this sort of adapter - see the potential problem section below. If youre interested in this approach you could always cobble yourself together an adapter using old body caps and other parts.
But in short I dont think that adapting a Canon FD lens to an EOS camera is worth the trouble for most situations. If you have a really expensive FD lens already Id probably be more inclined to use it with an FD-compatible body such as a nice used T90 or A1, unless you really need some unusual function supplied by EOS bodies. Or you might want to do macro photography with your digital EOS camera using old FD lenses.
So ironically enough, EOS cameras usually work better with non-Canon manual-focus lenses than with Canon manual-focus lenses. A shame, because Canon did build some very nice FD lenses years ago, many of which are available quite cheaply these days because the FD system was effectively orphaned by the introduction of EOS.
* Yes, it is true that Canon developed three AC series lenses which were basically FD mount lenses with autofocus motors built in. However, these lenses worked only with the Canon T80 camera and were essentially an evolutionary dead-end. So its not entirely inaccurate to say that all actual FD mount lenses are manual focus only.
Anyway, once youve got the lens attached youll obviously need to focus it. Unfortunately, Canon EOS cameras were never really designed with manual lens focussing in mind and so come equipped with focussing screens which lack any form of manual focus assistance. By contrast, many cameras from the 1970s and 80s featured split-circle and microprism focussing aids that simplified focussing a great deal.
If your camera has interchangeable focussing screens and if you find yourself doing a lot of manual focus work you might want to consider investing in a screen that can provide you with useful manual-focus feedback. The EOS 600 series, EOS 3 and all EOS 1 series cameras support interchangeable screens and split-circle viewfinder screens are available. EOS 5/A2/A2E cameras supported interchangeable screens, but no split-circle or other manual focus screens were ever made. The same with the EOS 5D - it has interchangeable screens, but no manual focus screens are forthcoming from Canon. However, users of recent digital cameras (EOS 10D, 20D, 300D and 350D) may find that a third party screen from Katz Eye or Haoda Fu will work. I have tried the Fu product and have a review of it on my Web site. I have not tried the Katz-Eye products.
Without a manual focus screen youre just going to have squint through the viewfinder and hope. Or buy an actual manual-focus camera that fits your lens. (or hack your camera to have a split-circle viewfinder screen if youve got a Rebel/EOS 1000 or Elan/100 camera) Note that the in-focus indicator in the viewfinder doesnt work unless the camera can communicate with the lens electronically, so you cant rely on that either, unless youve added a chip. (cloned versions of such chips are now available - a hobbyist sells them on eBay, for those of a tinkering bent)
Finally, once youve got your picture composed and focussed youll need to set the exposure settings correctly, and for this youll need stop-down metering.
What is stop-down metering?
Normally your EOS camera will meter the light using the widest aperture possible for the lens. (ie: the aperture diaphragm will be fully open - f/1.8 or f/3.5 or whatever the lens supports) This lets you look through the viewfinder with the maximum amount of light coming in. When you take a photo the camera quickly stops the lens down to your selected aperture just before opening the shutter. Canon EF lenses rely on electronically-controlled aperture diaphragms, not mechanical ones operated by the camera body via a cam or lever. As soon as the shutter has closed again and the picture has been taken, the lens diaphragm pops back to the widest setting once more.
There are two exceptions to this mode of operation. First, if your camera has depth of field preview and you have it enabled, the camera will stop down the lens aperture to whatever youve set it to be. And second, if you have a lens installed that doesnt have an electronically-controlled aperture diaphragm the camera will operate in stop-down metering mode - itll meter whatever the lens is currently stopped down to. Hence stop-down metering.
All Canon EF lenses contain a computer chip and various electrical connectors that allow the lens computer to communicate with the cameras computer. Most third-party lenses for EOS also have EF-mount compatible electronics. However, if you buy a lens designed for another camera system and attach it to your EOS camera using a lens mount adapter youre obviously not going to get the full electronic control youd get with a true EF lens. In particular, if there are no compatible electronics then neither autofocus nor electronically-controlled apertures will work.
But my EOS camera has no aperture lever!
Thats correct. Canon EOS camera bodies, unlike older mechanical camera bodies, do not have a mechanical lever to stop down the lens aperture when the photo is taken. Thats why you need a lens capable of maintaining your selected aperture setting at all times.
Some lenses have manual and auto settings that you may need to adjust. Others have small pins on the lens mounting ring that need to be held in at all times - check to see if your adapter ring keeps the pin in place.
If you have the manual for your lens see if theres a section on stop-down metering. What you dont want is the lens operating under the assumption that a mechanical lever inside the camera body will stop down the lens aperture at time of exposure.
Old and new stop-down metering styles.
The earliest Canon EOS cameras and the later models handle stop-down metering in two different ways. Its easy to tell which style your camera uses.
Turn your camera on and remove any lens that may be attached to it. With no lens attached to the bayonet press the shutter release down halfway and look at the aperture setting in the viewfinder or top-deck panel.
If the display reads 1.0 (or any number other than 00) then you have the old stop-down metering style.
If the display reads 00 then you have the new stop-down metering style.
How to use the old-style stop-down metering style (display shows something other than 00).
If you attach a non-EF lens to your older Canon EOS camera, the camera notices that the lens doesnt have a working computer and goes into stop-down metering mode. It nonetheless displays a full range of apertures, which you can set from 1.0 to 32.
Set the cameras aperture setting to 1.0 and leave it there.
Do not set the cameras aperture value to match that of the lens. In fact, I dont know why the camera lets you change the aperture setting at all, since it only screws things up by overexposing the image.
If your lens has an adjustable aperture (usually an aperture ring on the barrel) you must do the adjustment on the lens itself, not the camera. This will obviously vary the amount of light entering the camera. The camera reads it and meters from that accordingly.
Now, since the camera isnt capable of adjusting the aperture setting on the lens it cant work in P (program), Tv (shutter speed priority) or PIC (icon) modes with such a lens, but itll work just fine in Av (aperture priority) and M (manual) modes.
In Av mode you set the lens aperture using the lens aperture ring and the cameras aperture setting to 1.0 and then camera will set a shutter speed automatically. In M mode you set the aperture using the lens aperture ring and then set the shutter speed on the camera yourself.
One other note - some older EOS cameras have the annoying inability to remember aperture settings when you switch from one mode to another. Some models, such as the EOS 620/650 or 10/10s, automatically switch the aperture value to 5.6 whenever you go into Av and M modes. Since the aperture value must be set to 1.0 when using stop-down metering and a manual lens you have to dial the aperture back every single time you enter either mode. This is particularly annoying in M mode, because since these cameras lack a rear command dial you have to hold the partial metering button whilst rotating the main dial. Oh, well.
How to use the new-style stop-down metering style (display shows 00).
If you attach a non-EF lens to your newer Canon EOS camera, the camera notices that the lens doesnt have a working computer and goes into stop-down metering mode, displaying the aperture value 00. This means that the camera knows that the aperture setting is not under its control and will not let you set the aperture electronically. This metering style makes a lot more sense than the old method.
If your lens has an adjustable aperture (usually an aperture ring on the lens barrel) adjust it now. This will obviously vary the amount of light entering the camera. The camera reads it and meters from that accordingly.
Now, since the camera isnt capable of adjusting the aperture setting on the lens it cant work in the Tv mode with such a lens, but itll work just fine in the other creative modes - P (program), Av (aperture priority) and M (manual). It doesnt really make sense to use the lens in any of the PIC (icon) modes.
Set the aperture using the lens aperture ring and the camera will set the correct shutter speed in all other modes except M, where youll have to set the shutter speed yourself. Generally, Av mode is probably the most convenient.
Stop-down metering and manual focussing is pretty straightforward, but here are a handful of potential pitfalls.
Some users of wide-angle manual lenses, such as the MC Zenitar 16mm fisheye lens and various super-wide Leica lenses, have reported mirror clearance problems on some film and full-frame digital cameras. In other words the rear element (rear-mounted filter in the case of the Zenitar lens) protrudes out too far and physically blocks the cameras reflex mirror. If the camera locks up with a blinking battery symbol when you try to take a photo (and the battery is OK) then its likely that the lens is blocking the mirror.
If this happens you may have a fundamental incompatibility between the lens and camera body (particularly with Leica wide angles) or you may be lucky and may just have an issue with the lens adapter. For example, the people with problems with their Zenitar lenses seem all to be using an M42 to EOS mount adapter. My own Zenitar lens has an actual EOS mount attached to it, not the M42 adapter, and Ive had no mirror clearance problems. Its possible that the users of the M42 to EOS lens adapters havent fully tightened the lens onto the adapter ring, which could lead to problems. The EOS 5D camera is particularly vulnerable to wide-angle lenses colliding with its mirror, though I can report that the Zenitar fisheye works fine so long as you have the real EF mount on it - I cant say if the M42 to EOS mount adapter works.
Camera locks up with the manual focus lens installed.
Canon EOS cameras contain tiny switches in the lens mount which are used to sense the presence of a lens with autofocus electronics. If a manual focus lens trips this switch - perhaps through a badly designed lens mount adapter - then the camera will lock up because the switch is telling it to expect an electronic lens, but there are no electronics to be seen.
In such a case you may need to unlock the lens and rotate it very slightly so that the switch doesnt engage. If you do this dont turn it too far - or dont let it get bumped - because the lens might fall off!
A similar problem occurs if you install a teleconverter (extender) or extension tube between your manual focus lens and your camera. The camera will get confused and lock up because the autofocus lens switch is tripped but there arent any lens computers around. The workaround is the same as the above - unlock and rotate the lens and TC.
EOS 5/A2/A2E, Elan 7, 7E/EOS 30,33/EOS 7 metering problems.
The 5/A2/A2E (same camera; different names for different markets) and earlier Elan 7/EOS 30/33/7 camera (same camera; different names) do not meter correctly when a manual lens is attached - theyre typically a few stops out. Its really unfortunate that these cameras have this flaw, but there you go. Fortunately it appears that later model Elan 7/EOS 30/33/EOS 7 cameras have the problem fixed, and I am told you can take your camera to Canon to have to reprogrammed if you have one of the earlier models. I dont have any details on this, however - you would need to contact Canon.
If you know German you could also have a look at this page here, which provides some details on fixing the problems for the adventuresome. Essentially the process involves cannibalizing an old lens (the author used a defunct 35-70 zoom) and attaching the circuitry to an M42 adapter. If this seems too daunting you could simply try compensating for the error manually, though I hear conflicting reports as to whether or not the metering error is linear.
Dark image in the viewfinder.
Well, thats why I suggest you focus first! If youre setting the lens to a small aperture you may find the image in the viewfinder is too dark to focus properly.
Metering is slightly out.
Its possible you may have problems achieving completely accurate metering with your camera and manual lens. Since the camera has no way of obtaining lens characteristics from the lens it doesnt know what sort of metering compensation to apply. See also the issue with the FD adapter mentioned below or the issue of the Elan 7/EOS 30/33/7 mentioned above.
Its probably worth shooting a few test frames on digital, or a test roll of film, when you first put a manual lens on your camera to see if the camera is metering correctly for the lens. My Zenitar fisheye lens, for example, is generally OK but seems to be about a half stop out if wide open or fully stopped down. I find that Lensbabies manual lenses tend to be a whole stop overexposed.
Finally, it seems youre probably best off using partial metering (or centre-weighted averaging) over evaluative. Partial metering meters a smallish area at the centre of the frame rather than trying to apply metering algorithms based on metering individual segments of the whole frame. I dont know if its because the evaluative algorithms rely on information on the lens or what, but partial seems to be more accurate from the limited tests Ive done. Either way, be sure to test your own gear yourself first. See the note below regarding spot metering, however.
Metering problems with the Canon FD->EOS adapter.
Theres a remark from Canons Chuck Westfall about a problem with the Canon FD-EOS adapter and EOS cameras which lack interchangeable focus screens in the old EOS FAQ. Look for section 9.18 - Why are there limitations on the use of the FD->EOS Macro adaptor (sic) with some EOS Cameras?
Spot metering problems.
Apparently, and I dont have a camera for which this is an issue, some EOS cameras with spot metering (eg: EOS 1 and 1n) cant handle spot metering correctly with a manual lens adapted this way. Again, its probably worth doing a little test in the various modes before taking that once in a lifetime shot.
No adjustable aperture ring.
Some lenses do not have an adjustable aperture. For example, mirror (catadioptric) lenses have a fixed aperture - usually f/8. So the only ways to adjust the amount of light hitting the film are to adjust the shutter speed, use different film speeds or put a neutral density filter over the lens. This limitation results from inherent properties of the lens, and not from any lens to camera body adapter.
Incompatible aperture ring.
As noted above, some lenses, such as older Pentax M42 threadmount lenses, cant be stopped down manually or else require an EOS->M42 adapter that holds down a pin on the lens mount. Later Pentax threadmount lenses have a manual/auto switch that lets you determine whether or not the lens aperture changes when you turn the aperture ring.
If you cant stop down the aperture you may be forced to shoot wide-open all the time, which would be unfortunate since thats where the lowest quality of the lens tends to be.
Telescope focussing problems and the Scheiner disc.
It can be really hard to focus a telescope properly, especially when youre peering through a camera viewfinder. One useful trick is to cover the end of the telescope with a piece of cardboard or similar opaque that has two round holes cut into it. When you look through the viewfinder at a bright object youll see two dim ghost images. Adjust the focus until the images overlap, then remove the cardboard. Youll probably need to experiment with hole size and placement for this to work well. A typical suggestion is to put in a pair of holes each about 1/3 to 1/4 the size of the lens diameter, separated if possible by a distance equivalent to that hole diameter. (ie: both holes should be the same distance from the centre of the lens)
Such discs are called Scheiner discs, as they were invented by Galileos sometime adversary Christoph Scheiner (1573-1650), apparently in 1619. Theyre also commonly referred to as Hartmann or Shack-Hartmann masks, though Hartmann masks usually contain more than two holes.
The M42 threaded mount (the universal screw mount popularized by the Pentax Spotmatic camera) is similar to the Tamron T-mount - both mounts are 42mm in diameter. However, M42 lenses use 1mm threads and T-mounts use 0.75mm threads. This stupid decision on the part of Tamron (the M42 mount predates the T-mount) means its quite easy to wreck a lens or camera if you try to force the wrong type of lens onto the wrong type of camera, even though they look like they should fit.
So be very careful, and double-check with your dealer before you buy the lens adapter. Spotmatic-style lens mounts are usually called M42 or M42 body mounts, but sometimes T-mounts are referred to as M42 as well.
Battery drain with long exposures.
Most EOS cameras require battery power to keep the shutter open. This is obviously a problem for astrophotography, a field in which very long (many hours) exposures are quite common. Itd be really frustrating to have a picture turn out poorly because a battery drained flat in the middle of a 5-hour exposure. The risk is compounded by the fact that battery performance drops dramatically in cold temperatures, and its often very cold at night. Bob Atkins Web site has a useful list of the approximate battery life times for a number of EOS cameras, but note that it hasnt been updated to include newer EOS cameras. For example, the EOS 3 supposedly requires minimal battery power to stay open, but I dont have any hard data on it.
If battery drain is a problem for you, consider buying an EOS 10 or an older EOS 600-series camera. These first-generation EOS models dont need power to keep the shutter open. In fact you can disconnect the battery once the exposure has started and theyll stay open.
Im not sure about lenses. All EF lenses contain an electrically-controlled aperture diaphragm that requires power to open and close. Ive tested all my lenses (use depth of field preview to stop down the lens, then remove the battery) and they dont seem to require any power to keep stopped down, but its entirely possible that this varies on a lens by lens basis - test first. Obviously, a manual focus purely mechanical lens will not require any battery power at all to keep stopped down.
Adapting EF lenses to non-EOS cameras.
Well, having spent all that time covering the use of non-EF lenses with EOS cameras, how about the reverse? Can you take your favourite Canon EOS autofocussing lens and put it onto your Canon FD or Nikon or Pentax or whatever camera?
The short answer is no.
The long answer is that its probably sort of technically possible, depending on the camera body, but nobodys done it, as far as I know. More trouble than its worth.
As noted earlier in this document, EF lenses have complex electronic systems which are used to transmit aperture and other data from the camera to the lens. They dont have simple mechanical rings or levers to adjust the aperture. So using an EF lens without working electronics would be difficult. You could shoot wide open. Or you could stick the EF lens onto an EOS camera, set the aperture to whatever you want it to be and then remove the battery from the camera. All the Canon EF lenses Ive used will maintain their currently set lens apertures when you disconnect the power.
In theory I suppose that somebody could reverse-engineer Canons lens mounts and design an adapter gadget to send the proper electronic signals to EF mount lenses for manual aperture control, but it wouldnt be easy to do and it almost certainly would not be cost-effective to manufacture as a commercial product.
Focussing, on the other hand, shouldn't be a problem. Aside from a handful of A series (autofocus-only EF) lenses sold briefly in the late 1980s, nearly all Canon EF lenses can adjust focus manually by rotating a focus ring. Most are mechanically linked - either the focus ring turns a mechanical geartrain directly when the lens is in manual-focus mode or, in the case of USM (ultrasonic motor) lenses with FTM (full time manual) they turn a simple clutch ring setup. One exception is a handful of early USM lenses, primarily longer telephotos, which used a manual focus system that requires power. Such lenses, such as the 28-80 2.8-4L USM, have a manual focus ring which instructs the USM drive to rotate. These lenses couldnt be used, of course.
Finally, theres the matter of the actual adapter ring. And this is where things are very problematic. As far as I know no company has mass-produced adapter rings that let you attach EF lenses to other camera systems. The EF lens mount is quite large; larger than anyone elses 35mm lens mount. So youd need an adapter which adapts a large lens to a smaller camera mount. Then youd probably need optics to compensate for the register differences. If you hear of such a thing, please let me know!
Robert Monaghan maintains a huge page on the subject of lens adapters:
WJ Markerink has a list of specs for various lens mounts:
Information on Leica R, Nikon F or Pentax screwmount (M42) lenses on EOS:
A useful and growing list of M42 (screwmount) lenses known to work or not work with the EOS 5D camera:
Adapters for Nikon, Pentax screwmount (M42), classic Voigtländer lenses on EOS:
Adapters for Hasselblad, Mamiya 645, Pentacon 66, Pentax 645 and Pentax 6x7 medium format lenses on EOS:
Adapter for Contax lenses on EOS:
An Asian maker of various adapters:
Information on the hard to find adapters for Olympus OM lenses on EOS:
- NK Guy, PhotoNotes.org.
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