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02-24-2014, 04:04 PM   #1
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AF Fine Adjustment Settings

I'm still pretty new to all this, but last week bought a Pentax-D FA 100mm F2.8 WR Macro and ALL my autofocus shots were like mud. I bought a Datacolor SpyderLensCal SLC100 and determined (using tripods and leveling) that the lens back-focused so bad that on 10+ on my K5 it was still back-focused (but much less like mud). I got excited and calibrated all my lenses, maybe a mistake on the zooms - I can always take out the adjustment, but I have a couple of questions:

Once a good setting is established for a prime lens, will it need to be re-calibrated? What might cause it to need to be re-calbrated?

If I reset the camera to factory settings is all the AF Fine adjustment lost?

02-24-2014, 04:34 PM   #2
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QuoteOriginally posted by Gemvision Quote
I'm still pretty new to all this, but last week bought a Pentax-D FA 100mm F2.8 WR Macro and ALL my autofocus shots were like mud. I bought a Datacolor SpyderLensCal SLC100 and determined (using tripods and leveling) that the lens back-focused so bad that on 10+ on my K5 it was still back-focused (but much less like mud). I got excited and calibrated all my lenses, maybe a mistake on the zooms - I can always take out the adjustment, but I have a couple of questions:

Once a good setting is established for a prime lens, will it need to be re-calibrated? What might cause it to need to be re-calbrated?

If I reset the camera to factory settings is all the AF Fine adjustment lost?
If most of your other lenses are within a "reasonable" AF adjustment range (+/- 8 or so) and this one is +10 then you need to send the lens back.


Obviously if you need vast adjustments on most lenses (especially to the same side) you have a camera problem.



Just make sure you're doing the AF adjustment from a proper distance. I'm not sure how this changes with a macro, but for non-macro use here's the chart: http://michaeltapesdesign.com/lensalign.html
02-24-2014, 04:57 PM   #3
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QuoteOriginally posted by Gemvision Quote
Once a good setting is established for a prime lens, will it need to be re-calibrated? What might cause it to need to be re-calbrated?
The materials stretch and move with usage, both in lens as well as in camera. If they move "in opposite directions" you might need re-calibration.
I would say you should calibrate until you are happy with it. And if that is impossible or has to be done frequently, then you might want to send the lens back in (have it exchanged) or send it in with the camera for the shop to calibrate the two mechanically (though, this might require the equipment to be sent to Pentax HQ).
The DFA 100mm WR is a super sharp lens, it would be to bad to let its AF ruin shots. Just keep in mind that it has a relatively slow AF, especially in live view, so you should give it the time it needs. Macro lenses generally are not the best for AF, which is why some even have a focus lock function.
02-24-2014, 05:07 PM   #4
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Thanks, DSims.

Yes, the lens that could not be corrected is on its way back to KEH. All my other calibrated Pentax lenses backfocus 5, 7, 8 & 10. I don't think the camera remembers the settings for my Sigma lenses, but at least one of them front-focused.

Do the lenses need to be recalibrated once a good setting has been established?

If I reset the camera to factory settings is all the AF Fine adjustment lost?

Is there a way to make the camera remember my Sigma lenses - no data appears about them in EXIF when I use them....


---------- Post added 02-24-14 at 06:10 PM ----------

Thanks Na Horuk! That helps!!! I prefocused the 100mm and just used the AF for regular shots - only use manual for macro.

02-24-2014, 05:37 PM   #5
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Yes, the problem with third party lenses is that they use odd lens ID (or none at all) so the camera cannot always remember their individual adjustment. You can try compensating for those lenses with a global adjustment, and then use individual adjustments for the Pentax lenses.
And for my macro I even changed the AF function in the Menu. I removed the "Af on shutter press" and changed it so that the camera only tries to AF when I press the AE/L button on the back. This way its MF most of the time (since the lens has quickshift), but if I need AF, I just use my thumb.

---------- Post added 25th Feb 2014 at 01:37 ----------

Of course, this setting takes some getting used to.. I still sometimes half-press shutter and wonder why AF doesn't start!
02-24-2014, 06:50 PM   #6
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QuoteOriginally posted by Gemvision Quote
Yes, the lens that could not be corrected is on its way back to KEH. All my other calibrated Pentax lenses backfocus 5, 7, 8 & 10. I don't think the camera remembers the settings for my Sigma lenses, but at least one of them front-focused.

Do the lenses need to be recalibrated once a good setting has been established?

If I reset the camera to factory settings is all the AF Fine adjustment lost?

Is there a way to make the camera remember my Sigma lenses - no data appears about them in EXIF when I use them....
Good idea. Even if your camera's a bit off, I think this one is too far out of range.

Not sure about the Sigmas as I only have one Sigma lens (8-16) and I rarely use AF on it (but the distance scale is dead accurate at infinity, which is what really matters on that lens).


What I worry most about is how AF adjustments might potentially change after a firmware upgrade. I actually need to do a couple of those, and re-calibrate the AF adjustment for my lenses just to make sure (I think they need it anyway).
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