# AFMA for lenses with a max aperture of f/8



## Ardan (Jul 1, 2013)

Hi all,

I have been configuring afma settings for my lenses these past few days. A bit of a tedious job, especially because I had not done this yet for any of my lenses and so had to do it for all of them. I think it will pay of tough, especially for my 50mm f/1.4 .

I did (or tried to do) the last one this evening: EF 70-200mm f/4 IS L + EF 2x iii. On the wide end, the scale on the DataColor SpyderLensCal target was always entirely in focus, for any AFMA setting ranging between +3 and +9. While I can obviously live with this, I find it a bit strange that the AFMA setting has so little (or even no?) effect. On the tele end, there is generally a small amount of front focus, and again the AFMA setting seems to have little or no effect (at least over the range +3 to +11 which I tested).

Has anybody else had a similar experience? Is there a limitation to AFMA for f/8 max aperture lens/teleconverter combinations?

And another small question on the side: does AFMA have any effect on Servo AF? In DPP, the AFMA setting is listed for photos taken in One Shot AF mode, but not for photos taken in Servo AF mode.

Thanks in advance for your feedback!


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## neuroanatomist (Jul 1, 2013)

It's not surprising. I've noticed with FoCal that the slower the lens, the flatter the curve. An f/5.6 lens has a broad, fairly flat 'peak' on the graph, meaning a range of acceptable AFMA values. 

Yes, AFMA applies in Servo mode as well. I haven't looked in DPP (I use Aperture and DxO), but the AFMA value does show up on my 1D X's LCD for shots in Servo mode. 

Thinking about that more, I recall a discussion on this a while back. I use back button AF, and IIRC that might make a difference in whether the AFMA value is recorded in the EXIF in Servo.


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## Ardan (Jul 1, 2013)

neuroanatomist said:


> It's not surprising. I've noticed with FoCal that the slower the lens, the flatter the curve. An f/5.6 lens has a broad, fairly flat 'peak' on the graph, meaning a range of acceptable AFMA values.
> 
> Yes, AFMA applies in Servo mode as well. I haven't looked in DPP (I use Aperture and DxO), but the AFMA value does show up on my 1D X's LCD for shots in Servo mode.
> 
> Thinking about that more, I recall a discussion on this a while back. I use back button AF, and IIRC that might make a difference in whether the AFMA value is recorded in the EXIF in Servo.



Thanks for the quick reply neuro, that makes sense indeed.

I've followed the AFMA procedure you described in one of your articles on tdp. It was a very useful tutorial!


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## Halfrack (Jul 1, 2013)

f/8 with any real distance will end up with a big enough DoF that most alignment tools just won't be big enough. LensAlign http://michaeltapesdesign.com/lensalign.html has a super long model ( 32" ) for this size dof.


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