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12-16-2008, 02:08 PM   #1
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K20D Focus adjustment limitation

I know you can make the individual AF adjustments (for back and/or front focus) for AF lenses made my Pentax, and Pentax only.

My Sigma 24-60 needed an adjustment for front focus and now it is just fine (most likely it presents itself as a Pentax lens, I don't know; but it works). However, there seems to be no way to adjust my two other Sigmas as they are recognized as the "same" lens (that is 24-60mm). Unfortunately, the adjustment needed by the 24-60mm is just the opposite of the other two. When I mount them they start front focusing heavily due to the prior dedicated AF adjustment.

1) Does this mean simply that I can use only one of my Sigma lenses on my K20D?

I also have a K10D body which allows for global AF adjustment (and it needed that to correct consistent back focus with every lens). That adjustment works only to some extent (as long as all the lenses need the same/similar value).

2) Is there a way (as yet undocumented & undisclosed!) to make "individual" AF adjustments on the K10D? If yes, then I can use one of my other Sigmas on it...

I guess the answers are 1-Yes and 2-No.

Still, there is no harm asking

12-16-2008, 02:23 PM   #2
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1) What you said about K20D recognizing only Pentax lenses is not true. I have three Tamron zooms and one Tamron macro and it recognizes them each one individually. But if yours recognisez your two Sigma lenses as the same, then all you need to do is when you switch from the first Sigma to the second just set the focus correction for it in the menu and you are done. When you switch again, just go back into the menu and set the correction for that lens. All you have to do is to remember what is the correction for each lens.

2) The K10D can remember only one global setting. What I do is I have mine with firmware 1.1 and I either keep it in the debug mode and change the setting every time I change the lens. Sometimes if I want to keep a lens on it for a long time, I take it out of debug mode and then go back in it when I need to by using the push button sequense.
12-16-2008, 03:04 PM   #3
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Thanks, Stratario

Your first suggestion is very good actually. I know the values and there is no reason (other than the slight impracticality) why I should not do it.

Regarding your Tamrons' recognized individually; I guess Tamron either made an agreement with Pentax or they reverse engineer differently...

Your suggestion for the K10D is also useful.

My problem is perhaps that I like to play with the lenses too much; changing them frequently. They move from one body to the other. That is why I was after an "auto" solution Perhaps, pairing some lenses with a specific body and never mounting a certain lens to a specific body might also help...

Thanks for the helpful reply...

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