Katzeye Split Prism focus screen

Got my Katzeye yesterday and installed it in my T1i today. Do not try this without a good lighted magnifying lens if your eyesight isn't really good. I have a so-so lighted magnifier and it was a royal pain trying to see what I was doing.

That said, I did eventually get it installed properly and I think if I have to do it again, it would be easier. I'm fairly happy with the results. Below are some comparison images with 100% crops. These are SOOC with no corrections (as you can tell from the CA).

Auto focus and 100% crop.

Just don't bother to trust Spot mode metering with that in place, although you might get away with using it with the 50 f/1.4 and 85 f/1.8 lenses.

I did notice that it tends to over-expose in AV mode when shooting AF now. But using the MF it seems to work fine. Not sure I understand why switching the lens setting from AF to MF would make a difference like that. If it over-exposed everything, I'd blame it on the Katzeye (though they claim it doesn't affect AE). But since it works fine when using MF, I don't know what to think.

In any case, my goal here was to use this body for MF only and pick up a Roki 35mm f1.4 and 85mm f1.4. Those should work well with this screen. I have my 7D for everything else.

M_Six wrote in post #14304975
I did notice that it tends to over-expose in AV mode when shooting AF now. But using the MF it seems to work fine. Not sure I understand why switching the lens setting from AF to MF would make a difference like that. If it over-exposed everything, I'd blame it on the Katzeye (though they claim it doesn't affect AE). But since it works fine when using MF, I don't know what to think.

Katz Eye web site at one time (years ago) mentioned the situation in which metering error would be more likely, with as much as 3EV error reported by users.

On this page they state, "The treatment can increase the apparent brightness up to 2 stops or more in some conditions. " Since the metering is in the pentaprism and reads the focusing screen, it makes sense that changed brightness in the focusing screen can introduce error; and since the split image area is effective 'coarser' and passes less light than usual, that has error of its own.

In reading the specifics of the screen for the T1i, it mentions up to 2EV error with the Optibright treatment while in Spot mode, half way down the 'Product Details' page here http://www.katzeyeopti​cs.com …ng-Screen--prod_450D.html
Evaluative only has about 0.3EV error when f/5.6 lens is used, otherwise no error.

AF vs. MF ought not to have any effect on metering.

I didn't get the Optibright treatment. And the difference in exposure was with the 18-55 kit lens. My 85mm f1.8 worked fine in both modes, so I'm not sure what the issue with the kit lens was. It'll take some practice, I'm sure, but I think I can adapt to it. I just ordered the Roki 85mm f1.4, so we'll see how it works with that lens.

Just re-read the Katz Eye site the prior information was indeed about the non-OptiBright. They state that the OptiBright treatment does not alter meter accuracy. The kit lens does slow to f/5.6 at the long FL end of its range, so the 0.3EV error would apply, but that would NOT be so out of whack as to be clearly an error.

I had a katz eye screen with optibrite in my 20D that I moved to my 30D. I LOVED it. I did not notice any metering difference either.

I agree putting the screen In for the first time was a bit harrowing; but after I did it once it was a piece of cake the second time (Like sensor cleaning)