Originally posted by smc 
I just rceived a K85 1.8 and I have a KatzEye. The camera shows in focus and so does the katzeye....but the it's not quite there after I download the pic. Lighting is right and it should be fine being handheld (when I use DA* glass it's usually fine). I am hoping I can tweek the system to get it right or figure out what I am doing wrong....I have had quite a few great shot with my Taks and Ks..but it seems to be a constant fight.
1. Try controlled tests with a tripod first. Hand held cannot make any useful conclusion. At minimum focus distance of your lens, at f/1.8 the DOF is ~6mm. If you inadvertently rock forwards or backwards 6mm (1/4") then your focus point will be off. If you are pixel peeping, you would probably notice focus problem even if you moved less than 6mm.
2. f/1.8 is significantly more shallow than f/2.8. From you profile, it looks like all of your other lenses are f/2.8 or dimmer, so they are more tolerant of focus error. If you stop your 85mm down to f/2.8 then the DOF increases to ~10mm, which is significantly (70%) more DOF.
3. All lenses are slightly different, even when the split-screen is set up perfectly. I tested a number of my lenses when I installed a split-image screen. Some were more prone to back-focus, while others were more prone to front-focus. There was no one shim-thickness that was perfect with all my lenses, I had to use one that gave the best compromise between my most BF'ing and FF'ing lenses. So far, it's been acceptable. However, if I had tested only with one lens then it would have skewed my focusing.
4. Repeat, repeat, repeat. Even with a tripod, repeat each test a few times to get an average. At least 3 times, 6 is better. Out of 3 tests, I could sometimes see one image perfect, another FF'ing and a third BF'ing.
5. Focus direction/practice. I find when I focus from close-distance my images tend to FF. When I focus from far-distance, my images tend to BF.
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