Gear Talk > EOS Bodies - For Stills

How does Mk. III handle 2 micro AF adjustments?

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Z:
So... enough time has passed for a lot of users to have calibrated their 5D Mark IIIs.  I'm left wondering, out of curiosity's sake, how the new AFMA works. Let me expand on that...

With the new AF system in the 5D3/1DX, users can now provide 2 AFMA values; one for the long and one for the wide end of zoom lenses. Let's say for argument's sake my 70-200 worked best with +4 at 70mm and +12 at 200mm - does the camera scale the AFMA across the zoom range? (i.e. automatically guesses +8 at 135mm, halfway between the two extremes?).

I'm not sure how anyone would have this information, but I'd love to be enlightened.

neuroanatomist:
Thanks for posting this, I am also curious (in fact, I previously wondered about this).


--- Quote from: Z on May 01, 2012, 01:08:24 PM ---I'm not sure how anyone would have this information

--- End quote ---


The AFMA value is displayed on the LCD during image review, and written in the EXIF (can be viewed in DPP).  So, it would be as simple as applying to different values to the wide vs. tele ends of the zoom, taking shots through the zoom range, and looking at the AFMA that is applied.

Z:

--- Quote from: neuroanatomist on May 01, 2012, 01:35:22 PM ---... it would be as simple as applying to different values to the wide vs. tele ends of the zoom, taking shots through the zoom range, and looking at the AFMA that is applied ...

--- End quote ---
Excellent - in that case, somebody hook us up with some values!  ;)

bkorcel:
So far I have not had much luck using AFMA on the wide end as the DOF on the wide end typically does not allow for a good sense of how far focus may be off if any.  Any guess would be just that.  So far I have left the wide end set in the middle.

According to the documentation the camera will extrapolate AFMA between the two ranges for a zoom.

I do like the fact that it will register lenses based on serial numbers as well as extender combinations which is desireable if you have multiples of same model but dont have time to remember which lens was calibrated with which camera.

I've also found that trying to evaluate AFMA on the camera screen is not a good idea.  Transfer the raw image to DPP or photoshop and evaluate there.  Takes more time but it is much easier to evaluate without any guessing.

So I discovered that my 300 2.8LIS by itself and with 1.4x was front focusing by about 4.  With the 2X it was dead on.

70-200 2,8L IS II on the 200 side was front focusing about 2.

That's probobly within technical tolerances I would think.  Someone might be able to shed more light on that.

Mt Spokane Photography:
Looking at my AFMA test shots, the AFMA value is interpolated between the two extremes.
 
Thus, for my 28-300mmL, at
 
28mm, AFMA = -13
135mm, AFMA = -8
300mm, AFMA = 0

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