MFA problems

Just a quick check before my lens goes to the doctor

My recently purchased (used) 300f4 L is noticeably soft. I have microfocus-adjusted and get good sharp results when I do it, (I check on a computer screen, not the lcd).

Here's the workflow:
Mirror lockup, timer, tripod, set the focus through the in-camera menu, adjust the focus with AF on.
Push the 'set' button to register the lens after I finish, and take a test shot.

I've also done it tethered with Canon Utilities, same result, great test shot, adjustment doesn't register.

I don't press the shutter in between, so it's not reverting back to the soft AF point.

The camera doesn't seem to register the MFA changes, even though the MFA scale shows the adjustment. When I took test shots by manually focusing, the image was very sharp, so I know the lens can be adjusted.

Am I missing a step here? I'm going bald with all the hair-pulling, and it's not a good look on me,lol.

Any ideas appreciated.

I will try to be brief. Here is my most successful method:

It sounds like you are off to a great start, tripod, mirror lockup, etc.

I did not use computer software at all, found it to be inconsistant at best.

I setup my gear up outside about 4pm, good natural light and not overbearing.

I set my 'target', a clear water bottle about 3 feet away with my 24L II lens.
Imagining it was a face, and a spot on the label was their eyes.
Because this is exactly how I intended to use the lens, NOT as MFD
90% of my photos are environmental portraits (people doing things at places)

I started at -10 -5 0 +5 +10 MFA values
Set to center point only USING VIEWFINDER!!!
Set to -10
Take 1st shot turn MF ring
Take 2nd shot turn MF ring
Take third shot, turn MF ring (to ensure refocus between MFA values!!!)
Set to -5 and repeat


Got a set of 15 shots total, sometimes awaiting consistent (but real-world) lighting conditions.
Finished, packed up, went inside.

Loaded all 15 to the computer.
Knowing that they were in sets of 3 for each value. 3, 3, 3, 3, and 3 = 15
Immediately upon viewing the sets at 100% I knew -10 -5 were WORSE
0 was ok and so was +10 but +5 was great! Better than 0! (default)

Retested the next day between +4, +5, and +6 and +5 was perfect.

Hope this helps you. Good luck.

* NOTE you can check the MFA on the photo itself using the LCD on the camera tapping the info button after taking the shot to unsure that you are confirming the MFA value change, not canceling it between shots.


* One last note, the further your subject is from your lens, the more pronounced each MFA value is.
Credit to another member's advice for MFA adjustment tip.
I doubled my working distance when testing +4, +5 and +6 solely for testing reasons.
It was MUCH easier to see the correct adjust to make.

Thanks for the excellent rundown Infinite, especially the last bit about distance from lens. I will do that tonight and see if I can improve the results.

I'm horribly embarrassed to admit this, but I finally found the reason the MFA would not seemingly 'register' on the camera - (a step that not one single article of the many I had pored over made mention of) - is that you have to disable the microadjustment after pressing the set button before taking a shot, as the camera reverts back to the original AF setting. Maybe that's just in the 50D?

Something that never occurred to me as I though it meant disabling the MFA adjustment itself while shooting...

No that is how it works on my 7Dmk2 and 5Dmk3 Use to drive me nuts when I would forget