Comments on MFA

[Colin500]

Hi Everybody,


a couple of weeks ago I finally took the time to perform some micro-focus adjustments for my lenses, after all, being able to do an MFA was one reason why I upgraded from the 500D. Here's my thoughts on the subject:


- Every lens required some adjustment, unsurprisingly the 50mm f/1.8 II with +12 the most, the others a lot less, but all in the same direction, perhaps the body is off.


- There is a remarkable improvement, even a +3 or +4 makes a world of difference in AF accuracy with thin DOFs, I am only now really happy with my glass.


- It's a scandal that MFA isn't standard on _every_ DSLR (hello, I'm looking at _you_ 60D), how many millions of people shoot unnecessarily crappy images with their Rebels just because the AF is bad?


- The procedure is relatively easy, at least I made it so, just printed out some detailled pattern, hung it on the wall, and played a bit with magnified live view.


- That said, I don't understand why the camera can't do it automatically, once it's set up with an appropriate target, using the normal contrast-detect method to check the real AF, that's exactly the same thing that I did "manually".


(I'll check the Canon SDK to see whether I can programmatically set the MFA, and force a focus-to-infinity, the rest shouldn't be that hard.)


Regards, Colin


PS: Nice to have the forum back up-and-running, the nightly server problems were translating to "forum offline in the afternoon" for me; I've also been busy with many other things...

[scalesusa]

I do think that its a worthwhile feature, and for wide aperture lenses with a shallow depth of field, it makes a huge difference with just a small adjustment.


Out of the dozens of lenses I

[HDNitehawk]

A few Saturdays ago it was raining and I decided to go through most of my lens (all the primes) and check the MFA to see if I could improve. With both 5D Mark II the only lens that really seemed to improve with adjustment were the 24mm F1.4L and the 35mm F1.4L. But what I found was that if I did the MF at a certain distance, then backed up several feet and did it again, the adjustment would be off by a bit. After playing with this for hours I ended up with +-0 on both lens.


Maybe others might have thoughts on this, but it seemed that it only fine tuned to the distance you might be shooting. (with the 24 and 35mm). Other distances and conditions would vary and the adjustment would change. Another thing I noticed with the 5D MarkII is that it would be less likely to hit the exact same mark depending on the position the focus was at on the lens at the time you begin to auto focus. This was true with both 5D

[Daniel Browning]

I prefer the acronym AFMA (AutoFocus MicroAdjustment) over MFA (Micro Focus Adjustment).

[bob williams]

I prefer the acronym AFMA (AutoFocus MicroAdjustment) over MFA (Micro Focus Adjustment).
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Daniel, Please explain? You usually have valid/technicalreason for your thoughts and opinions, But I can't figure this one out.


Thanks,


Bob

[Daniel Browning]

No big deal, really; it