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11-02-2010, 08:53 AM   #31
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K10d has more and more backfocus while it ages Got it solved through service menu. the K-5 i have now has no problems with any lense indeed. Relief!!

11-02-2010, 09:34 AM   #32
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QuoteOriginally posted by Andi Lo Quote
Thanks for the info. My k10d is focusing perfect with all my lenses right now thankfully (and they're sharper than ever like you said). I won't be deterred going to K5 because of this issue anyway I'll just send the lens to pentax if this occurs in the future (knock on wood).
That's great! I would have done the same. I asked Pentax about sending in my K10D with the lenses I wanted it calibrated for. (I think they can set up one body for five different lenses.) But Pentax wouldn't do it for a non-Pentax lens, and my favourite lens is a Sigma 24-135 I'd probably still have my K10D if Pentax would have calibrated it. (I wasn't so interterested in having to hack my K10D and leave it in debug mode to do it myself.)
11-02-2010, 10:08 AM   #33
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QuoteOriginally posted by Class A Quote
By "smaller company" do you mean the one that produces the "LensAlign" tool?

Have you got information about the ColorVision Focus Calibration tool? I can only find a store that sells it but with zero info about the product. (except the price). EDIT: Is it this "SpyderLensCal"?
Yeah that is it... I know nothing about either product. Just thought people on here might like to know about them.
11-02-2010, 02:48 PM   #34
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QuoteOriginally posted by StigVidar Quote
AF works by measuring phase differences on light entering the lens on the left and right side in two small spots. These spots are at a distance equal to about f/5.6. Problems start to appear when lenses are misaligned. The AF system could then measure perfectly in-phase light, but an image could still be out of focus on the sensor or the focus screen.

Here are 17 pages with technical information: http://www.dougkerr.net/pumpkin/articles/Split_Prism.pdf
So global adjustment is for misaligned body and individual alignment is for messed-up lenses.
Now it makes more sense. Thanks.

11-16-2010, 02:34 PM   #35
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QuoteOriginally posted by Ex Finn. Quote
So global adjustment is for misaligned body and individual alignment is for messed-up lenses.
Now it makes more sense. Thanks.
So my conclusion is, if I have to do adjustmens for a particular lens on a body, then it seems to be wise to return the the lens to the shop or send it in for warranty repair. Keeping such a lens lowers its value, because it is kind of defective.
However, if I have an old lens then I can be happy if I can correct FF/BF problems in the body.
11-16-2010, 02:46 PM   #36
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QuoteOriginally posted by cbaytan Quote
In my knowledge is (might be wrong though), AF system including an AF sensor is different from the image recording sensor, and AF system tells the lens where to stop. A micro-metric wear or misplacement on the lens' screws or aligning point makes the lens stop at the wrong place. Thats my guess.
This is correct. The focusing sensor may set the point of maximum sharpness either in front of or behind the recording sensor. The same can happen with manual focusing. What looks sharp to the eye may still not place the focal point on the exact plane of the sensor. It is for this reason that focus calibration is so valuable. On my K-7, all of my lenses required some adjustment. Once accomplished, I could not believe how sharp they are.

Rob
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