Focusing

[cbarron30]

6d mark 1
5d mark 3
I just recently bought a new 50mm 1.2. On my 6d I was able to get good focus after micro adjustment at -10. On my canon 5d mark 3 it’s still seems to be off at -20 and is not as sharp as the 6d. I used the spyder lens cal and a tripod make sure I am 25*50mm back (about 50inches) I also shot wide open at 1.2.
Thank you

[cbarron30]

Is this a lens problem or my 5d? Thank you

[RobertTheFat]

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@cbarron30 wrote:
Is this a lens problem or my 5d? Thank you

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If it's either, I suspect it's a lens problem. A MF deviation of 10 is pretty high. (The farthest I've had to go is 9.) And you're saying that on the other body it's worse.

But you have to keep in mind that the 50mm f/1.2 is a tricky lens with a very low DOF at maximum aperture. You may want to play around with it a bit more before you send it in. Are you able to get accurate focus manually?

[cbarron30]

So ya on my 5d it’s way worse. 

The picture below is at 0 microadjustment

[cbarron30]

 This is at -20

[cbarron30]

I haven’t really tried manual yet. I know DOF very low but I just feel like it’s not as sharp or on point with it’s autofocus as it should be. ( I know it’s not the sharpest lens either) thank you for your reply!

[ScottyP]

Are you testing wide open at f/1.2 for the shallowest possible DOF?  There's an oddly large amount of the scale in focus in the second photo.  Nearly the whole ruler. 

Could be a fluke of the curved focal plane working in accidental combo with the out of whack focus, on the slanted scale, I suppose. 

[Waddizzle]

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@cbarron30 wrote:
6d mark 1
5d mark 3
I just recently bought a new 50mm 1.2. On my 6d I was able to get good focus after micro adjustment at -10. On my canon 5d mark 3 it’s still seems to be off at -20 and is not as sharp as the 6d. I used the spyder lens cal and a tripod make sure I am 25*50mm back (about 50inches) I also shot wide open at 1.2.
Thank you

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Making AFMA adjustments should be done with care.  It is much easier to make bad adjustments than correct ones.

I perform adjustments at 50x the focal length, and at minimum aperture.  You should use lighting that is similar to the conditions that you expect to encounter when you use the lens.  I am certain that bright streak of light, which appears to be coming from a window curtain is not helping matters.

If you have any filters on the lens, you should remove them for the AFMA testing.  

You should take several test shots and average the results.  Take a shot, and then defocus the lens.  Defocus the lens both in front and behind the target.  If your results do not show a consistent trend, like a consistent amount of back focus, then you could be introducing error in your measurements.