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Notes on Haoda Fu’s manual focus viewfinder screen for EOS digital cameras.

PhotoNotes.org DonationsCopyright © 2005 NK Guy

http://photonotes.org/reviews/viewfinder-screen/

Disclaimer

First, I’m going to begin this review with a full disclosure statement. Every other review on this Web site to date has been of a product for which I have personally paid full retail price. This has more to do with the fact that nobody has ever provided a product to me for the purposes of reviewing than anything else, but it hasn’t harmed my determination to write honest and (as much as is possible) unbiased reviews. Still, if Canon or anyone else were to be inclined to let me use some of their gear for review purposes I wouldn’t, of course, object, assuming they in turn wouldn’t object to me writing what I consider to be a truthful and honest review.

Anyway. The point is in late 2005 I was contacted by Mr Haodu Fu regarding his line of viewfinder screens. And so the product I am reviewing here was provided by Mr Fu at no cost to me. As always, I intend to write about it honestly and accurately, but I also believe in the importance of disclosing this sort of thing, so there we go.

Why manual assist screens?

Next, a little history lesson. Years ago, in the days before computerized autofocus systems, people obviously had to focus their cameras by hand. About the first visual assist systems to help with this task were ground sheets of glass. Light from the lens was cast onto the surface of this glass and the photographer would adjust focus while examining the projected image.

Ground glass screens work okay, but they can be difficult to use in lower light conditions and also require time and experience to use well. So camera makers developed other manual focus assist aids. Various devices were invented over the years, but by the 1970s most SLRs had microprisms in their viewfinder screens. These were tiny prisms etched onto the viewfinder surface. When viewing an in-focus image the picture in the microprism area tends to be broken up into tiny triangles.

Another popular assist aid was the split circle or split image system, which used two larger prisms. By the 1980s most SLRs had a split circle with a ring or collar of microprisms. Split circles are just that - the centre of the viewfinder has a circular area bisected by a line, usually horizontally. (though sometimes diagonally) You find a vertical line in your picture and adjust focus until the line appears unbroken in the split circle. If your subject lacks high-contrast vertical lines then you can try using the microprism collar.

However, by the late 1980s autofocus systems were becoming workable for SLR cameras. And SLRs basically use computerized versions of the split circle system - phase comparison - internally. However, camera makers apparently decided at that point that autofocus was so wonderful that nobody would ever want to focus manually again, because they took the manual focus assist aids out of their camera viewfinders. Canon left them in as an option with the initial 600 series of EOS cameras - you could replace the generic viewfinder screen with a split circle one - but after that only the EOS 3 and EOS 1 series of cameras supported optional manual focus screens.

Add-on viewfinder screens

So. That’s all well and good if you autofocus all the time. But what if you do like to manual focus occasionally? What if you use a manual focus lens? Perhaps you use a Canon TS-E tilt-shift lens, which is manual-focus only. Perhaps you use an adapter ring to attach your favourite old manual focus lens (maybe an old favourite Zeiss or Pentax lens, say) to your camera. Or maybe you’ve hooked up your camera to a telescope. In all these cases you’ve basically been out of luck if you shoot EOS but don’t have a professional-series camera. Most EOS cameras don’t, in fact, have easily interchanged viewfinder screens at all.

In the mid 2000s, with the rise of affordable digital Canon SLRs, two American entrepreneurs introduced viewfinder screens that could be installed in these cameras. One is Haoda Fu, a photography enthusiast. The other is Rachael Katz, with the Katz-Eye line of products. And it’s Mr Fu’s viewfinder screen for the EOS 10D camera that I’m reviewing here. I received a screen with a horizontal split, though Mr Fu also sells a version of the screen for the 20D with a diagonal split - useful for situations where you can’t find a convenient vertical line to focus on.

The Fu screens are sourced from commercial products apparently originally intended for Minolta cameras. He has arranged to have them cut down and carefully machined to fit various EOS cameras instead. At time of writing he sells replaceable screens for the EOS D30, D60, 10D, 300D/Digital Rebel/Kiss Digital, 20D and 350D/Digital Rebel XT/Digital Kiss N cameras. He does not maintain his own Web site as such, but does provide online support via his Yahoo group Web page. As noted, I installed one into my EOS 10D.

The screen.

The screen arrived in a flat bubblewrap-lined shipping envelope. It was inside a small plastic envelope packed inside a flat plastic case designed for storing AAA batteries - good sturdy hard plastic. It was clean and free of obvious dust, but did not come with any instructions.

This is the main point that will cause some concern for less experienced users. The cameras in question were not designed to have user-replaceable screens, and the documentation downloadable from Mr Fu’s Web site is geared specifically towards the 350D. You can get plenty of email support if you have any questions, and Mr Fu has been very responsive to other user’s queries, but installing the screen is not as simple as attaching a new lens or something like that.

Indeed, you’re messing around with pretty delicate components when you install a screen. Besides the plastic screen itself, which is etched with extremely fine and easily scratched lines, there is the mirror assembly and the underside of the pentaprism. All of these components can be damaged by a slipped tool. If you aren’t comfortable with this level of fiddly work you may want to consider paying a local camera shop to install the screen for you.

Installing the screen on a 10D.

On the 10D it was a matter of positioning the camera upside-down. There are two metal tabs with small rectangular holes punched into them visible around the bottom of the mirror box. These are the visible parts of the springy rectangular metal clip which holds the viewfinder screen in place. You use a small pair of tweezers (ideally plastic or plastic-coated so you minimize the risk of gouging the viewfinder or mirror if you slip up) to push the clip inwards to release it. With both tabs released the clip lifts straight out.

At this point you should have two more items to remove. There’s the plastic viewfinder screen itself and there’s a thin brass shim which Canon use to ensure that the viewfinder screen is correctly calibrated. Tilt the camera so they flip out of the space in which they rest and remove both of them. (or three of them if your camera happens to ship with two shims) I’d highly recommend marking the bag you place them into indicating which is the mirror side and which is the prism side so that you minimize the risk of putting things in backwards if you choose to replace them at some future date.

The Fu screen does not look the same as the Canon original. The Canon screen has five tiny tabs sticking out which are used for alignment. The Fu screen does not - it instead has two long tabs which run nearly the full length of the two narrow sides. These tabs are created by the machining down of the plastic sheet, suggesting the viewfinder is basically a cut-down screen from a full-frame camera. Rather, the Fu product has the same outer configuration as the brass shim piece, and it does seem to fall neatly into place when it’s installed. It does not ship with a brass shim and in fact Mr Fu advises that you remove the existing shim when you install his screen.

The plastic tabs go in towards the front of the camera body - it should be easy to tell as you simply go by the configuration of the brass shim. The screen’s shinier side faces the mirror mechanism and the not so shiny side faces up towards the prism assembly.

A useful site with illustrated instructions on installing the screen is maintained by Joe Hawblitzel. Fu’s own directions are available from his site as a PDF, but I found them a little less clear.

The shim and focus accuracy.

The removal of the brass shim is controversial. It’s clear that the shims are there so that Canon has the ability to adjust the focussing of the viewfinder at the factory to a high level of precision on each camera they ship. Some people have argued that, by not using this shim, the Fu product may run the risk of introducing error on those cameras which fall outside the average.

Mr Fu defends his product, arguing that the vast majority of 10D cameras do not need this precise level of shimming (though 350Ds do and thus his 350D screen retains the shim) since they nearly all ship with the same size shim. He also claims that a significant factor in his decision not to support the shim is that the delicate metal part is frequently damaged upon installation, and that a bent screen shim could easily introduce focus errors. He adds that nobody has complained about focus error resulting from the use of his product. Not everyone is comfortable with this explanation, though admittedly some of the critics have not actually used his product. Apparently the competing viewfinder screens take a different design decision - they are machined to the same thickness of the original Canon screens and have the same tab configuration.

I have not used the Katz-Eye product and so am not in a position to compare them. I can say that I haven’t noticed any focus errors with the Fu screen. The limited tests I’ve done have shown that manual focus with the screen in place looks good and any variations are probably due to human error more than anything else. In fact, on one of my lenses (an EF 50mm 1.8 mark I) the manual focus operation seems more accurate than the autofocus, which is interesting.

People wanting to see a more detailed discussion of the issue may want to have a look at this discussion thread on DPReview. At the very least it offers some interesting insight into the personalities of Mr Fu and Ms Katz and some of the more vocal users of their products.

Metering.

Metering can be a problem with replacement screens since the transmission of light through the new screen is different and Canon never designed their consumer/midrange cameras to support screens other than the default factory-issue version.

I did not notice any significant metering problems with Mr Fu’s screen, but I have to admit that I have not done any heavy testing and comparison with the original Canon screen. I just installed the replacement screen and took a load of pictures. This is totally not scientific, and I make no representation that you won’t have problems if you use the same product. I have heard that there are metering issues when using the Katz-Eye screen, particularly with slower lenses and with partial metering, which in my opinion would be a significant drawback. Having to apply exposure compensation in partial or centre-weighted averaging mode but not evaluative would be very inconvenient. Here’s a DPReview post from someone who has tried both products and confirms the situation from his experience.

Autofocus indicators.

Another big drawback of putting a manual focus screen in an EOS 10D is that you lose the autofocus indicator points in the viewfinder. Normally the currently selected autofocus indicator is displayed as a glowing red rectangle when you peer through the viewfinder. Unfortunately these rectangles are etched into the surface of the viewfinder screen itself. So you lose in-screen verification. You keep the autofocus confirmation light, since it’s a green dot to the lower right side of the screen, and a bit of red light does leak through around the edge of the focus circle if you have the centre point selected, but that’s it.

You do get to see which focus point you have selected if you look at the top deck LCD while selecting the point, but that’s obviously considerably less convenient. And you can scratch in marks in the correct positions - or mark up the screen with a graphite pencil - yourself, but that's going to look a bit messy. I typically use just the centre point except when using flash, so this isn’t enough of a stumbling block for me not to want to use the screen, but the inconvenience is definitely a strike against the product. (admittedly through no fault of its own)

Luckily users of the 20D don’t have this problem. The 20D has a separate screen with the autofocus indicators etched on it, so you can replace the focus screen while retaining these marks - a considerable advantage.

Screen brightness.

It may be simply that the Fu screen is slightly less textured, but it did seem very slightly brighter than the default Canon screen. Doesn’t make a huge difference either way, really. Certainly there’s no loss of brightness, which is a good thing since the 10D does not have a very bright viewfinder.

Prism blackout.

One drawback of using any microprism or split circle assist with telephoto lenses is that with long or slow lenses you will find the assists tend to black out, making them more or less useless. Sometimes you can move your head around to adjust the angle of your eye relative to the incoming light, but basic optic geometry dictates that such manual focus assist systems are definitely limited by the angle of incoming light. Most screens of this type tend to black out at f/5.6 or so.

Luckily I didn’t find this a massive problem with the Fu screen. I put a 100-300 5.6L with a 1.4x Kenko teleconverter on my 10D and was still able, barely, to use the split circle screen - but only with hugely high contrast subjects. It was a bit inconvenient, but luckily autofocus seemed to work okay - I was shooting a solar eclipse with a solar filter in position, so the subject was indeed very high contrast - so I didn’t need to rely on manual focus at all.

I’ve never been a huge fan of microprism, though. I had to use microprisms in my old Pentax Spotmatic, and never liked them much. The only time I find microprism collars at all useful is in really dark situations when there’s no vertical line to focus on. For example, I found the microprisms worked reasonably well when achieving focus on a night scene illuminated by small incandescent lamps - photographing palm trees in a Tunisian oasis lit by small lamps. The high contrast of the lights made using the microprisms fairly effective.

Using the screen - conclusions.

Overall, if you love split circle focus assists like me, then I recommend this product. I’ve really enjoyed split circle focus ever since I first used the method on a Canon A-1 SLR. It’s simple, intuitive and incredibly fast. There’s something rather satisfying about the simple act of lining up the two semicircles on the screen. And with an autofocus camera it’s fun watching them line up automatically when I’m using AF. (though a bit disconcerting sometimes, as the Canon AF system doesn’t always agree with the manual focus alignment)

So on the whole I really like having this viewfinder in place. I do enough work with manual lenses (such as a Zenitar 16mm fisheye lens and a Lensbaby) and with situations in which autofocus is challenging or non-existent (such as with extension tubes in place) that I find I do benefit from the manual focus assist. It’s great to have that extra level of control if you need it. I do miss the autofocus point lights on my 10D, but that’s a price I’m willing to pay.

So. Thanks to Mr Fu for providing me with the screen for this review. In my experience the screen is quite functional, not too difficult to install, and a good investment if you find yourself doing a lot of manual focus work on your digital EOS camera. I am aware of the no-shim controversy, and it may indeed be an issue for some users on some cameras, but I myself did not notice anything problematic with the Fu screen in place. Perhaps my camera is average enough in its shim requirements that this isn’t a problem - I can’t obviously state that accurate manual focus isn’t going to be an issue for anyone else.

Finally, if you found this review of benefit in deciding to purchase the product, please let the seller know.

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