90D Autofocus help

clbayley

EOS 90D
Aug 28, 2016
162
30
Hello CR!

I am playing around with my new 90D on my 100-400L verII. I am trying to dial in the autofocus, as I am not seeing crisp eyes in my bird photographs.

For all the AFMA experts out there, I have attached a picture of the calibration target. I would appreciate some help interpreting it...

For reference, shooting conditions were:

f/5.6 2sec ISO 100
Tripod mounted about 20ft from target at 400mm
10sec timer release
Lens stabilizer turned off
ONE SHOT AF mode
Single AF point locked on to the small circle beside the ruler

This is my first attempt at using this calibration ruler. Honestly, nothing looks terribly crisp, though the best seems to be between 0 and 1.

All interpretations are very much appreciated!

Regards,

CB
 

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Mt Spokane Photography

I post too Much on Here!!
CR Pro
Mar 25, 2011
16,600
1,564
You are pretty close, the recommended minimum distance is 25 X the focal length or just over 32 ft. Sixty Four feet would be optimal. You'd want a larger target at the longer length. That target is not really intended for 400 mm lenses. You can set AFMA at 20 ft if that is the distance you shoot. Lenses tend to front focus a little at close distances, so it might be very good at 65 ft. Unfortunately, that usually means you must setup outdoors for very long distances.

The lens is front focusing a slight amount, I suggest taking 10 images while setting the lens to mfd before each shot. You may find it does not focus exactly the same, you should not set AFMA based one one image. Also take images using live view in the same manner. Most or all of those should be focused correctly.

I had a lens align tool, but when FoCal came out, I pre-ordered it, its much easier to get accurate adjustments.

Here is one using my 100mmL using live autofocus which is generally very accurate. The sharpest focus should be on or near the "0".

The camera alignment to the target is critical. Notice the hole in the center with a red surround? It will be red if you are not aligned correctly.

100mmL%20Contrast%20detect-1.jpg
 

navastronia

EOS RP + 5D Classic
Aug 31, 2018
665
767
I'm sure you know this and I'm speaking the obvious, but trying to AFMA at f/5.6 on an APS-C sensor is going to be difficult in the first place because of the large depth of field. Wishing you luck - I have been through this headache before and didn't enjoy it.
 

AlanF

Stay at home
CR Pro
Aug 16, 2012
7,748
8,462
Hello CR!

I am playing around with my new 90D on my 100-400L verII. I am trying to dial in the autofocus, as I am not seeing crisp eyes in my bird photographs.

For all the AFMA experts out there, I have attached a picture of the calibration target. I would appreciate some help interpreting it...

For reference, shooting conditions were:

f/5.6 2sec ISO 100
Tripod mounted about 20ft from target at 400mm
10sec timer release
Lens stabilizer turned off
ONE SHOT AF mode
Single AF point locked on to the small circle beside the ruler

This is my first attempt at using this calibration ruler. Honestly, nothing looks terribly crisp, though the best seems to be between 0 and 1.

All interpretations are very much appreciated!

Regards,

CB
2sec? What's it like in liveview under the same settings?
 
Last edited:

AlanF

Stay at home
CR Pro
Aug 16, 2012
7,748
8,462
I'm sure you know this and I'm speaking the obvious, but trying to AFMA at f/5.6 on an APS-C sensor is going to be difficult in the first place because of the large depth of field. Wishing you luck - I have been through this headache before and didn't enjoy it.
What! I have been AFMAing this lens for years at f/5.6 on a large variety of bodies and it's a real doddle! The dof of a 400mm lens at 25x its focal length on APS-C is ±6cm at 10m. On FoCal I get beautiful fits every time. I had no problem doing my two 100-400mm IIs on my new 90 using the manual method as FoCal was not yet ready for its semi-automatic mode. Took about 15 minutes per lens doing duplicates. The 1.4xTC at f/8 is a different matter.
 

Mt Spokane Photography

I post too Much on Here!!
CR Pro
Mar 25, 2011
16,600
1,564
I'm sure you know this and I'm speaking the obvious, but trying to AFMA at f/5.6 on an APS-C sensor is going to be difficult in the first place because of the large depth of field. Wishing you luck - I have been through this headache before and didn't enjoy it.
The DOF is fairly shallow and should be no big issue. Its 0.06M or 2.4 inches in front and in back or a total of ~5 inches at 10M f/5.6 and 400mm. At 20 ft, its less than a inch.



dof.jpg
 

clbayley

EOS 90D
Aug 28, 2016
162
30
I really appreciate all your comments! I kinda knew that I needed more distance for the 400mm...but I did run into the small target problem too.

You have reminded me that I have a Focal account, so I ran my combo through that software a few times. Still on the short side, but Focal was giving me a consistent answer.

Once again, your collective knowledge has helped me out. Thank you.

CB
 
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Mt Spokane Photography

I post too Much on Here!!
CR Pro
Mar 25, 2011
16,600
1,564
I really appreciate all your comments! I kinda knew that I needed more distance for the 400mm...but I did run into the small target problem too.

You have reminded me that I have a Focal account, so I ran my combo through that software a few times. Still on the short side, but Focal was giving me a consistent answer.

Once again, your collective knowledge has helped me out. Thank you.

CB
Test it out at a longer distance and compare to live autofocus. If they are the same or very close, there is no need to worry about long distances.
 
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