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02-19-2015, 11:28 AM   #1
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FA* 200 / 2.8 IF AF adjustment in K3

Last Sunday took my new K3 for a spin with several lenses, Including my FA*200/2.8. This lens has been working flawlessly in my K20D for years without a problem, nor needed micro AF adjustment for the K20D.

But on my new K3, something was wrong with the pictures. I noticed that my "target" subjects in frame were not that sharp, but behind them, some things appeared to be in focus. So I set up a focus testing chart (homemade), placed it at roughly the closest focusing distance for the FA200 (which is about 4 feet) and shot a few frames usint IR remote with mirror up, at f2.8.

Surprise! My lens was backfocusing? So went into the C menus in camera, selected "single adjustment" and started doing some tweaking. I finally got it dialed in at +8 (only 2 more clicks left!!!!)

I know I got it dialed in right. After that, did some tests and the lens is showing razor sharpness all over again, but a couple of questions arise from this:

1) Isn't the +8 adjustment like "too much" for a FA* lens? Does it seem right?

2) Is it normal for a single lens to focus properly in one body (K20D) and needs adjustment in another (K3), considering the rest of my 13 lenses all focus perfectly without adjustments in either body?

3) What happens in case I get another FA*200/2.8; will the K3 apply the same correction for both or will it know the difference?

Here's my AF adjustment images.

Attached Images
 
02-19-2015, 11:30 AM   #2
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it looks like you over corrected. look at the 4s. you are front focused now.
02-19-2015, 11:38 AM   #3
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QuoteOriginally posted by wibbly Quote
it looks like you over corrected. look at the 4s. you are front focused now.
+1 - the trouble may be that it is between two settings. I have seen this before myself.
02-19-2015, 11:41 AM   #4
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It looks like a slightly smaller adjustment would be sufficient since the numbers on either side of the 0 should be equally blurry. BTW, make sure the focus test chart is properly aligned, otherwise your adjustments may not match up with real-world images.


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02-19-2015, 11:42 AM   #5
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QuoteOriginally posted by rburgoss Quote
1) Isn't the +8 adjustment like "too much" for a FA* lens? Does it seem right?

2) Is it normal for a single lens to focus properly in one body (K20D) and needs adjustment in another (K3), considering the rest of my 13 lenses all focus perfectly without adjustments in either body?

3) What happens in case I get another FA*200/2.8; will the K3 apply the same correction for both or will it know the difference?
Answers:
1 - No; as I understand it - the absolute numbers aren't based on lens quality. They are based on how the focus mechanism interacts with the lens.

2 - Yes; I haven't seen details of this in my own lenses because my older body wasn't easy to tune. However I have seen lots of posts from people that require different settings on different bodies.

3 - I think each lens has a unique identifier not just model info that the camera tracks but someone else will need to confirm this.
02-19-2015, 11:43 AM   #6
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QuoteOriginally posted by wibbly Quote
it looks like you over corrected. look at the 4s. you are front focused now.
QuoteOriginally posted by UncleVanya Quote
+1 - the trouble may be that it is between two settings. I have seen this before myself.
Looking closer, I guess you are right. I over did it. I will just go back to body and dial up a +5 and shoot some tests. It will probably end up there or maybe at +4. Now it doesn't sound like "too much adjustment", but still bugs me.

Thanks for your comments
02-19-2015, 03:47 PM   #7
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Every camera body and lens is built to a +/- tolerance.

Whether or not a particular body/lens combination needs AF adjustment is just luck - and the sum of the tolerances!
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