1D mark III AF microadjustment

I tried the chart at 45 degrees method and each calibration was giving me different results.

I also tried the diffraction pattern method on a monitor, same inconsistencies.

Finally this is the method I devised to adjust all my lenses on my Mark 3.

I printed 10 sheets with a pattern and number at the edge for about one inch.

Each page had a number from 1 to 10.

Then each page was mounted on foamcore (3.16 inch thick).

All the panels were then assembled on top of each other stagering them by one inch so the pattern and number was visible.

The contraption was then taped together.

To calibrate, I mounted this on a wall with fun tack.

I then placed my camera level with the middle of the assembly.

Then at the widest aperture for each lens, I focussed on the number 6.

This method makes the focus easy to see because the pattern is at a 90 degree angle from the camera plane.

I calibrated all my lenses and those needing adjustment showed the improvement right away.

This is the only method that permitted me to get consistent results when I repeat the calibration.

I hope my explanations are not too confusing.

I can post a diagram is someone is interested.

Jean

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That's a very nice idea. Only critique I have is that the number to focus on is rather small. To avoid mistakes it should be a twice as large as middle AF rect in when focusing. Even larger when you test focus from different distances and wide angles.

How many steps in microadjustment you need dial to move AF from one target sheet/plane to another?

I found that 2 step is very noticeable.

I think that if you can have your most critical focus within 3 sixteen of an inch , it's really good and having a smaller number of steps avoids errors of interpretation.

It worked wonders for me on the following lenses:

17-40L 4.0, 50 1.4, 85 1.2L, 24-70L 2.8, 70-200 2.8IS, 100 macro, 100-400L 4.5-5.6, 300L 4.0IS, 400L 5.6, 300-800 Sigma 5.6.

They are now all tack sharp.

Jean

What distance from the camera to the test sheets did you use? Same for all lenses? I am going to try this today. Thanks for the help.

I apologize in advance to the OP. I really do not intend to hijack the thread or in any manner dismiss his technique.

This is the easiest way - not claiming it is better than another, ultimately - to tweak the micro focus I've yet found.

On my 1Ds Mark III and a 24mm f/1.4 prime, I was 17 points off and bewildered by back focus - not any more.

http://www.openphotogr​aphyforums.com/forums/​showthread.php?t=4708

regards,

chmod

I used a similar method using books as the targets.

This is a shot of a wallpaper design at ~1m after I finished calibrating a lens. The first shows the focal point. The second shows a crop of the focal point area. It was shot as iso 800 (which I did not notice) so there is some noise.

This lens was significantly front focusing before the adjustment. This feature is far more useful than I anticipated.

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That is an excellent method. Almost makes me want to go through all the trouble to do it haha. I just setup dominoes instead

Thanks chmod for the link. I calibarated my 4 lenses:

85mm 1.8 - 0 (perfect)
24-70 2.8 - +7
70-200 2.8 IS - +11
100-400L - +12

You're welcome. It took me less than an hour to fine tune my five lenses. And, other than the 85 MII, they were all off.

regards,
chmod

HI CHWORKER,

I set up the camera at minimum focus distance for each lens.

chmod, I am not offended at all, if anyone has a easy and fast method I want to know about it.

I hope your results are as good as mine.

One thing to note is that I adjust all my lens so the focus range is about 1/3 forward and 2/3 back. I don't think that the computer interference allows this.

Jean

ticounne wrote in post #5168294
I set up the camera at minimum focus distance for each lens.

I've read (several places) that Canon adjusts focus at 50 X focal length. Hmmm....

-js

chmod wrote in post #5167557
I apologize in advance to the OP. I really do not intend to hijack the thread or in any manner dismiss his technique.

This is the easiest way - not claiming it is better than another, ultimately - to tweak the micro focus I've yet found.

On my 1Ds Mark III and a 24mm f/1.4 prime, I was 17 points off and bewildered by back focus - not any more.

http://www.openphotogr​aphyforums.com/forums/​showthread.php?t=4708

regards,

chmod

just used this one on 3 of my lenses:

24-70 turned out to be +3
70-200 2.8 IS was +8
85mm was +14

going to try it with my 120-300 when i get it back from calibration tomorrow and see how much micro I need to do.

I've tried a couple of methods, I usually end up around +15 for my 100mm f/2.0.
When I use the lens in a real time situation, indoor basketball, I always end up
putting the adjustment back to "0" cause the pics look soft and blurred. Back at
"0", they are not razor sharp, but I didn't expect that wide Open and 1600 ISO.
They seem much better than at +15???? Still experimenting with this.

Joemt