[BigMackCam]

I have all of my lenses calibrated on my K-3 and K-3II. Remarkably, the adjustments were identical for both cameras, suggesting that both bodies came off the production line with the same AF sensor adjustment (lucky me ).

Recently, I bought a "new / old stock" Samsung GX-10 (K10D clone), and I've worked out the AF adjustment values for two of my lenses - the FA50 f/1.4 and Tamron 28-75 f/2.8 (obviously I can only have one value set at any time, as the GX-10 / K10D doesn't support adjustments for multiple lenses).

On the K-3, the FA50 requires +2 adjustment, and the Tamron needs -4; while on the GX-10, the FA50 is best at +030 and the Tamron at +090. This confused me a little... it suggests that a +1 increment on the K-3's AF fine adjustment is equivalent to a -10 increment on the GX-10 (ie. the AF adjustments move in opposite directions for each camera)

Does anyone know if this is the case? If I'm correct, I'm hoping I can interpolate my GX-10 AF adjustment values using the table below - at least as a starting point for each lens. It would save me a lot of time...

Thanks in advance

EDIT: I just tried my DA35 f/2.4... On the K-3 it requires -3 adjustment, so I set it to +080 on the GX-10 and it seems to be more-or-less accurate; needs more testing, but it seems to work. I'd still appreciate any feedback, though, to make sure I'm not suffering from "confirmation bias"

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Last edited by BigMackCam; 10-23-2016 at 09:38 AM.

[JohnX]

Interesting, but...

My understanding is that AF Fine adjustment is actually compensating for two variables simultaneously; the manufacturing tolerances in the body AF system AND the lens.

If correct the fact that you've found the adjustments in your K3 and K3II bodies to be the same is purely coincidental and cannot be extrapolated into a rule for all bodies.

[othar]

Interesting, but...

My understanding is that AF Fine adjustment is actually compensating for two variables simultaneously; the manufacturing tolerances in the body AF system AND the lens.

If correct the fact that you've found the adjustments in your K3 and K3II bodies to be the same is purely coincidental and cannot be extrapolated into a rule for all bodies.

He is using the same lens on both/all three camerabodies, therefore the manufacturing variance of the lens stays constant and he can extrapolate the needed corrections for his other lenses in the way he described.

[BigMackCam]

He is using the same lens on both/all three camerabodies, therefore the manufacturing variance of the lens stays constant and he can extrapolate the needed corrections for his other lenses in the way he described.

Right, that's what I was thinking (whether it's correct or not is another matter). What I'm trying to ascertain is if a +ve increment on the K-3's AF fine adjustment is equivalent to a -ve increment on the GX-10 / K10D and vice versa (it appears to be); also, are the adjustments linear? If they are, then using the adjustments for two lenses on the K-3 and GX-10, I should be able to work out the GX-10 adjustments for the rest of my lenses, given the values on the K-3...

[JohnX]

He is using the same lens on both/all three camerabodies, therefore the manufacturing variance of the lens stays constant and he can extrapolate the needed corrections for his other lenses in the way he described.

You're absolutely correct. My bad!

[UncleVanya]

Right, that's what I was thinking (whether it's correct or not is another matter). What I'm trying to ascertain is if a +ve increment on the K-3's AF fine adjustment is equivalent to a -ve increment on the GX-10 / K10D and vice versa (it appears to be); also, are the adjustments linear? If they are, then using the adjustments for two lenses on the K-3 and GX-10, I should be able to work out the GX-10 adjustments for the rest of my lenses, given the values on the K-3...

For your copy that may be true. It is possible that it is not true for others. Imagine that the tolerances are different and another body is shorter or longer. The 0 spot would be different.

[BigMackCam]

For your copy that may be true. It is possible that it is not true for others. Imagine that the tolerances are different and another body is shorter or longer. The 0 spot would be different.

Yes, agreed - but once you know that zero spot (as I think I do, given the relative adjustments for both lenses on both cameras), is it reasonable to assume that a +1 incremental change on the K-3 is equivalent to a -10 incremental change on the GX-10?

[othar]

Yes, agreed - but once you know that zero spot (as I think I do, given the relative adjustments for both lenses on both cameras), is it reasonable to assume that a +1 incremental change on the K-3 is equivalent to a -10 incremental change on the GX-10?

Your testing seems to support your conclusion, so why not. I don't have a K10D but according to the user review section it doesn't support Front/back focus corrections, so maybe Samsung adapted the firmware differently than Pentax on their later camerabodies.

[BigMackCam]

Your testing seems to support your conclusion, so why not. I don't have a K10D but according to the user review section it doesn't support Front/back focus corrections, so maybe Samsung adapted the firmware differently than Pentax on their later camerabodies.

Thanks, Patrick. With the K10D and GX-10, you can get into a debug menu through a couple of "back doors" (the method depends on which firmware version is installed). Within that debug menu is an AF adjustment facility. Sadly, it only allows one setting at a time, but it's better than nothing