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View Full Version : Ec-L Cross-split prism focusing screen (my experience)


Dawid Loubser
April 30th, 2007, 02:14 AM
http://www.adorama.com/images/Product/CASECL1.jpg

A few days ago, I installed the Ec-L focusing screen in my 1D MkIIN, and my experience since has been very enjoyable and educational. If you have a varied shooting style, I wouldn't leave this in my camera 100% of the time, but I have a feeling I will leave mine in 90% of the time.

The accuracy and speed with which you can manual-focus on subjects, even in the worst possible light, is astounding. I regularly shoot in situations without flash (at ISO3200) where the camera's autofocus sensors do not function at all, and this has been a revelation for me. This especially applies to quite wide angles (I shoot up to 28mm) where the standard mate becomes very difficult to use, especially since I only have f/3.5 at 28mm (I regularly use the Canon 28-300L).

I have found, however, that at telephoto lengths this screen becomes less and less useful, and most importantly, this focusing screen does not like apertures smaller than f/4. (it's near useless at the f/5.6 my lens has at 300mm, as one or more of the quadrants go completely black).

My standard "walk around" lens is often Canon's 100mm f/2.8 Macro, and I have to say that the Ec-L together with this lens is pure bliss. It totally enhances the experience of looking through this combined high-precision optical instrument.

Autofocus, of course, still works (as it doesn't go through the focusing screen in the first place) and I've had no problems with exposure, although using spot-metering with the centre spot is not recommended. Not nearly as bad as some people claims, but centre-weighted-average still works 100% for me. If you use autofocus all the time, however, stick to the standard matte (Ec-III) as the matte around the central prisms on this screen is not great at all.

So, in short, I will not use this daily for wildlife, sports, etc. Rather stick to the mate + the fabulous autofocus. However, for "fine art" / street / people, this screen is amazing.

Many of you may know this, but I though I'd post this to somebody who's considering this focusing screen. As long as you have a reasonable fast lens, this is the most fun you can add to your camera for $40 or so. Totally worth it. I'm planning to try out some of the other screens available in the future.

Asher Kelman
May 1st, 2007, 10:26 PM
A great post. Could you describe the steps to change the screen. Do you use shims and how do you calibrate focus.

Asher

Will Thompson
May 1st, 2007, 10:54 PM
A great post. Could you describe the steps to change the screen. Do you use shims and how do you calibrate focus.

Asher

You insert the Canon screen tool, tilt the tool and click the screen is on the tool. (the tool looks like a disposable razor)

Swap out the screen on the tool and reverse the process, click it is in.

You do not calibrate anything. it is a standard Canon screen, focus is no different than with the one you replaced!

Asher Kelman
May 1st, 2007, 11:05 PM
Will,

Are you sure there is no adjustment possible?

Well that's not what I was told by Brightscreen™. They said they used shims to adjust the light path. Go figure!!

Asher

Dawid Loubser
May 1st, 2007, 11:45 PM
No adjustment is possible (or, shall I say, indicated by canon) as the screen precisely fits into the frame, and it's already perfectly calibrated for the camera body.

Since the BrightScreen screens are actually trimmed-down medium-format screens, I can see how they might need some calibration, as they are a (small) third-party outfit. I've never actually used a Brightscreen, but after using the Canon one, I am of the opinion that one of the tauted features of the Brightscreen, i.e. a disproportionally large split prism, would actually bother me. I feel the canon one is perfectly sized, but sometimes it almost "gets in the way", as (in the prism area) it doesn't at all give you an indication of what the image will actually look like (what the Depth of Field will be) since everything in the prism is in focus. So I often move the subject around to check what it would actually look like on the surrounding matte. I would not want a larger prism, the canon one is perfect for edge alignment. Also, I have heard complaints of BrightScreens being off-centre (i.e. not precisely aligned) which could also be distracting. The canon one is 100% perfectly aligned.

I didn't post any info regarding the insertion process, etc, as this is totally straightforward with the canon-supplied tool and instruction manual. The only real issue is that you must be sure to never touch the matte surface, as it is in fact practically impossible to ever clean any form of liquid or oily residue from it (understandable considering the microscopic structure).

As stated before, I'm still considering whether I like this in the 200mm+ range (probably not) but it's fantastic for 28mm to around 100mm with f/2.8+ lenses - depending on your style of photography, of course. But this screen allows me to focus accurately in conditions as low as 1/5s shutter at ISO3200 at f/2.8. On the original matte, everything is almost black, whereas the split prism circle seems to block no light whatsoever - it's like a bright and accurate dot in the middle of a dark viewfinder. Lovely.

(again, sorry for sounding like an excited amateur, but this is a new experience for me - I've always used cameras with matte or microprism screens before - both of which only "scatter" out-of-focus areas)

John Craig
May 2nd, 2007, 03:18 PM
I have a Beattie Intenscreen Grid + Split Prism.. haven't had any issues with focus adjustment. It's a little bit busy with the grid, but I love it.. works from macro to landscape (nice being able to verify straight horizons). Although CW has been recommended, I usually get away just fine with Evaluative metering, perhaps with a slight EC bump needed.

Grid also helps a bit with quick n'dirty idea of how to frame for squarer format final repro (ie. 8x10 or such vs. the 2:3 standard).

Alan T. Price
May 5th, 2007, 10:34 AM
However, Brightscreen may have replacement focus screens for cameras like the 20D that do not officially have interchangeable focus screens, and for them an adjustment shim may be needed.

I've used several Canon screens on the 1D2, 1V and 3 and they have never needed adjustment for anything but exposure.

Note that focus screens affect manual focus and exposure but not auto focus. MF is only affected if the matt surface on the screen does not line up with the usual focus screen plane and that should not happen if the matt surface is on the viewfinder side of the screen (because then screen thickness is not an issue).

Exposure is affected in two ways:
one way is that the overall surface texture that is needed for displaying an image causes some light loss. For different textures canon has a custom function that adjusts exposure readings. The brighter smoother screens show more of the scene in natural focus but are less "snappy" or selective than the darker coarser screens.

The second way the screen affects exposure is that special non-matt parts such as prisms will go dark (maybe even black) if there is not enough light. This is obviously affected by lens aperture but is then aggravated by the use of tele-extenders or filters or anything else that reduces light transfer. If only a small area is affected then metering is not affected much unless you are using spot metering at the "wrong" sensor (i.e. at the central sensor). Some prism screens are more suitable than others at handling darker apertures without blacking out.