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01-11-2011, 11:12 PM   #1
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BF with 2 lenses DA 16-45 & DA 50-135

In order to get my DA 16-45 to focus and the shutter to work at 16mm wide end, I had to adjust the fine focus to +10. I then tested the DA* 50-135 and had to adjust it up to +10 as well to get rid of most of the BF.

Is this normal as it seems a bit extreme when both lenses need such an adjustment to get somewhere near accurate focus and it is still a bit off towards BF?
Mike

01-11-2011, 11:31 PM   #2
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Which camera body are you using? Different models have different scales.
01-11-2011, 11:34 PM   #3
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K-5

Mick
01-11-2011, 11:55 PM   #4
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QuoteOriginally posted by aussiemick Quote
K-5

Mick
No, that's not normal - a few lenses might have this, but not most. If you're AF adjustments are accurate, the lenses probably should be sent in for repair - possibly the K-5 too.

However, I will say that at first I thought my DA*50-135 AF was way off on my K-5 - I had it adjusted to at least + or - 8 (+8, IIRC) by testing in indoor lighting. Then I went out and shot a holiday parade on a sunny day and most of my shots were out of focus. About 2/3 into the parade I realized that I should set the AF adjustment back to 0, and the shots came out much better from then on. Some of the earlier shots had to be fixed with Focus Magic before I could submit them for posting on the parade web site - a fairly time-consuming task!

Since then I've done more thorough testing using this tool:

Michael Tapes Design - LensAlign - WhiBal - IJFR - Michael Tapes: photo news and commentary - LensAlign MkII - NowShipping

Now it appears that the correct adjustment is -2. Since you have a K-5 with quality glass, the US$80 investment in this tool might be worth it. Shipping costs are fairly low since it comes disassembled in an envelope.

The latest (1.02) K-5 firmware has also helped my AF performance overall. Additionally, other sources say indoor lighting, or light less than about 3 or 4 EV, makes a difference in focusing accuracy on the K-5.


Last edited by DSims; 01-12-2011 at 12:01 AM.
01-12-2011, 04:24 PM   #5
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I think the problem is OK. Try adjust all + adjust one, which can give you +20 adjustment.

Focus adjustment on zoom lenses sometimes gives different results at both ends(i.e. maybe FF at one end and BF at the other end), if that's the case, then send the body together with the lenses to repair.
01-12-2011, 04:28 PM   #6
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Shang,
I am not aware of how you adjust lenses, could you give me some clues.

Mike
01-12-2011, 07:11 PM   #7
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QuoteOriginally posted by shang Quote
I think the problem is OK. Try adjust all + adjust one, which can give you +20 adjustment.

Focus adjustment on zoom lenses sometimes gives different results at both ends(i.e. maybe FF at one end and BF at the other end), if that's the case, then send the body together with the lenses to repair.
Page 127 of Pentax K-5 manual suggests that, if an [Apply All] value is set, the [Apply One] values are ignored.

I seem to have similar AF issues with both 16-50 and 50-135 lenses; the wide end on both of them seems to focus closer than the long end. However, an adjustment of +2 (in Apply All mode) seems to level the focuing to a usable degree. Too early to tell for sure though, as I am in the process of achieving perfect focus. (By the way, my K-5 does not appear to exhibit the low-light FF problem unless used in very low light, around EV 1).
01-12-2011, 07:12 PM   #8
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Aussie, you can adjust your lenses by doing some very simple tests(not scientific but they do work well). For DA* 50--135, you can simply turn off the Shake Reduction, then fix the camera and point it to a specific subjuct, such as a book. Then set the lens to f/2.8, take a group of 4 simple pictures using LIVE VIEW, at 50, 70, 90 and 135mm respectively. After that, the most simple way is to take 11 groups of pictures(each group has 4 pics at 50, 70, 90, 135) setting focus adjustment to 0, +1, +2, ..., +10. Then look at the pictures and find which group is the best compared to the LIVE VIEW group.

01-12-2011, 07:13 PM   #9
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QuoteOriginally posted by aussiemick Quote
Shang,
I am not aware of how you adjust lenses, could you give me some clues.

Mike
Lots of information in these two links:

AF microadjustment for the 1Ds mark III, 1D Mk3, 5D Mk2, 7D

https://www.pentaxforums.com/forums/pentax-dslr-camera-articles/61385-autofoc...ent-hints.html
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