Quick and Dirty AFMA

[dgatwood]

I have a feeling AFMA is a kludge at best, as I found it is somewhat distance and light-level dependent.
e.g. With dot-tune AFMA, my experience is that focus is spot on most of the time with the same distance and light-level as the calibration condition. When I take it outdoor with much brighter light-level, AFMA still helps but not as much as the darker calibration condition.

It shouldn't be dependent on light level, per se, except that with brighter light, you and/or the camera are typically using a smaller aperture, resulting in more depth of field, so small errors in focus have less of an apparent impact on the photographs.

You should always do AFMA in manual or aperture value mode, with the lens wide open. Otherwise, you're likely to undercorrect.

 

[PhotoCat]

It shouldn't be dependent on light level, per se, except that with brighter light, you and/or the camera are typically using a smaller aperture, resulting in more depth of field, so small errors in focus have less of an apparent impact on the photographs.

You should always do AFMA in manual or aperture value mode, with the lens wide open. Otherwise, you're likely to undercorrect.

I used full manual operation all the way with aperture kept at f1.8 for my 85mm for example. Only shutter speed and ISO was changed. It was just a feeling that light-level had a bearing on AFMA value but I have no scientific proof. Could be something else but definitely not aperture or DOF related.

 

[candc]

It shouldn't be dependent on light level, per se, except that with brighter light, you and/or the camera are typically using a smaller aperture, resulting in more depth of field, so small errors in focus have less of an apparent impact on the photographs.

You should always do AFMA in manual or aperture value mode, with the lens wide open. Otherwise, you're likely to undercorrect.

I used full manual operation all the way with aperture kept at f1.8 for my 85mm for example. Only shutter speed and ISO was changed. It was just a feeling that light-level had a bearing on AFMA value but I have no scientific proof. Could be something else but definitely not aperture or DOF related.

there are lenses that focus differently under different light. i have a sigma 18-35 that is impossible to calibrate because it front focuses more as the light and contrast go down. i have pretty much given up on using standard af wide open in poor light and low contrast conditions. i just use live view instead. still better than manual focus i reckon?

 

[DominoDude]

I've started running ML on my 7D now, and decided I should re-adjust my Sigma 50/1.4 EX DG HSM using the Dot-tune method. (I have some 4-5 other lenses that will be tested soon, so we'll have to wait for the final verdict.)

Expected the lens to be off. Did 3 runs to make sure I got a somewhat stable and reliable outcome from the test. The first was done slightly closer than the following - a few inches closer. The last two of the tests were done from the exact same angle, same light on the target, just a bit further away.
Here's the result:
1) +26
2) +33
3) +32

Test shots taken afterwards to confirm that I've finally nailed the correction of this b*tchy lens... Nope, the shots looks worse than if I set the correction values to +/-0, and they certainly doesn't look good there! Anyone with ideas on how to make the Dot-tuning turn out better?
Or should I do one more round at the distance (shoulders and up portraits) where I'll typically use this lens, with another kind of target, and then superglue the focusing ring and the AF<->MF switch into MF-mode? *foaming at the corners of my mouth*

 

[Loswr]

Anyone with ideas on how to make the Dot-tuning turn out better?

I got my money's worth for dot-tune...I found it to be inconsistent and therefore unreliable. I've been happy with Reikan FoCal.

 

[DominoDude]

Anyone with ideas on how to make the Dot-tuning turn out better?

I got my money's worth for dot-tune...I found it to be inconsistent and therefore unreliable. I've been happy with Reikan FoCal.

If you are right about Dot-tune being inconsistent and unreliable it could match my old doorstop, eh, Sigma.
FoCal - Yeah, I've never heard anything but good on that solution. It's definitely a route I will go when/if I get some income trickling in again in the future.

 

[rpt]

or use Magic Lantern Dot-Tune AFMA 8). I have had excellent & repeatable results

You've had better success than me, I found dot tune to be somewhat unreliable.

I have not tried it but that is exactly what J.R. said in another post... Since I use Reikan Focal and am happy with the results I don't think I'll bother.

 

[siegsAR]

I've read everything there is about dot-tune and was very hopeful I could have the same success like lots of people who used it from countless forums.

Result? So inconsistent w/ my 70D and the 4 lens I have. Its good some find it useful and works for them, but for now I've reverted back to the 0's.