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09-20-2012, 02:25 PM   #1

Focus screen (split screen)

Hello all,

I have gotten my self a K5 with the two WR kit lenses six months ago. Recently I also got an ME. In the mean time I have a collection of old lenses, all MF, some A-type, some preset (mir-1) some long range (300mm F5.6). They all fit fine on both cameras.

Now I am considering to invest in a catzeye split screen for better manual focussing on the K5. I read about the black out on using slow lenses.

Can you say that if there is no black out with the lens on the (FF) ME, that will also be no black-out on the (APS-C) K5? Does sensor size influence this? What other issues can I expect?


09-20-2012, 03:14 PM   #2
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I don't think the blackout is affected by the sensor size, its just that a lens that is slow is also dark and the screen can dim the image further. It depends mostly on what type and quality the focus screen is. But maybe someone who has that same katzeye screen can tell about their experience with very slow lenses.
09-21-2012, 03:01 AM   #3
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F5.6 is close to where the darkening starts. For best results, I'd recommend using F4 lenses or faster if you do opt for the split-screen.
09-21-2012, 06:20 AM   #4
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Hey there.

Sensor size has nothing to do with blackout. You could yank the sensor out of the camera entirely and the focusing screen wouldn't care.

I have the Katzeye with Optibrite & I use it on a K-x with an f8 500mm mirror lens with no blackout, so I think you'd be fine.

Good luck & happy shooting!
Bobbo :-)

09-21-2012, 10:50 AM   #5
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Split prism focus screen blacking out has more to do with your shooting environment than anything else. Point the lens at a dark subject in the shade in low light situation, you can see signs of split prism darkening at f4.0. The same lens pointed at a subject bathed in light during bright mid-day, may not show darkening effect until f16. Generally, a split prism focus screen will not show darkening effect that's detrimental to accurate focusing @ f8.0 for probably 90% of the lighting conditions.

My setup: KatzEye split prism focus screen in a K20D with O-ME53 viewfinder magnifier and various M42 and mirror lenses.
09-21-2012, 12:01 PM   #6
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I can verify that there is some darkening, but no noticeable blackout on the Katzeye even up to f/8 as long as you get the Optibrite version. At f/11 I can start to see some blacking out, but with good eye position it's still even usable at f/16.

One other thing to consider though is it does cause metering inaccuracies particularly with spot and center weighted metering. I use a hand held light meter for both spot and incident metering, so I couldn't care less, but if you rely on the camera's internal meter, you may have to get used to using exposure compensation to correct it. Some time spent with a gray card should tell you all you need to know.
09-23-2012, 06:58 PM   #7
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I have the KatzEye split-image screens, both with enhanced coatings, in my K20D and my old Canon DSLR. I rarely get blacking out. I use many slow lenses and set-ups where the focus confirmation won't function and I am able to see the point of focus. One slow lens I use regularly is my Celestron 1000mm f11 Maksutov-Cassegrain mirror lens (aka C90). I bought both screens during KatzEye's 10% off sales for about $105 each.

Do have a great day,
09-25-2012, 05:01 AM   #8

Thanks all,

All my MF lenses are either manual aperature (M lens type) or preset type. For both I can focus wide open and meter closed. I understand that is not a problem as long as I don't spot-meter or compensate.

I will consider the catzeye...

Thanks again


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