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10-20-2010, 06:34 PM   #1
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Trouble with the 31ltd - inconsistent AF and purple fringing

I am using a K20D with a Katz-Eye (no optibrite) and AF on the 31ltd has been very inconsistent. At first I thought there was something wrong with the lens( maybe there still is?) but I have gotten sharp results wide open, just not often. Anyone else with a similar problem?

And purple fringing is pretty shocking. Here's a example:

PS Having trouble uploading ("please check the file size" - it's within limits like always??)

Last edited by DanielT74; 10-20-2010 at 06:41 PM.
10-20-2010, 06:49 PM   #2
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Oh well, somebody's going to post it, might as well be me:

"It's the lens, and it's not fixable. Send it to me and I'll make sure it gets disposed of properly."

With that out of the way, I'll actually try to contribute something useful.

The KatzEye screen doesn't matter. Metering is read off the focus screen, but autofocus occurs entirely independent of that. It sounds like you might need to dial in some lens-specific autofocus calibration.

There are many threads in this forum about how to do that -- have you tried shooting some focus-test charts in natural light?

I can't help with the purple fringing complaint. I have heard of it before on the 31 Ltd., especially wide open, but some others here might be able to tell you whether your example is out-of-line or not, once you're able to get it posted.
10-20-2010, 06:57 PM   #3
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Mine has inconsistent AF too if it makes you feel any better. What I have found is that this lens is very picky on focus (AF or MF). It shows green/purple fringing even with the slightest focus error.
10-22-2010, 09:52 AM   #4
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I agree wit the PP, the FA 31mm focus is picky , especially at f1.8.

10-22-2010, 11:38 AM   #5
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just try to avoid shooting wide open during high contrast situations or harsh lighting conditions. stop down one aperture or two (f2.8 and f4) and you should be fine.
10-26-2010, 02:58 PM   #6
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I now get much better results since I switched the focus to Auto rather than on the Center or Select where I usually have it. Anybody else with similar effects?

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