I am so sorry but this is not working out for at the moment.

The field of focus is so narrow for example the 200mm f2.8 that each time

I look for the Moire , each time seems a bit diffrent and indications on barrel

are not consistent.

Hi Ralph,

Let's try to get this one solved, by using a workflow that should allow to get your AF Microadjustment close to perfect on average (there will still be some variation, but no bias). I also have a 200mm f/2.8, so I understand the difficulties with the narrow DOF range and one cannot utilize 'post-it' notes due to the distance scale being under a non-rotating window. By the way, this also demonstrates that maximum sharpness only exists in a very narrow range, narrower than the final DOF we may tolerate.

My lens (200mm F2.8 L USM) was serviced and focus is now better but the guy there still didn't get it a 100% to my liking. It still seems to be front focusing.

Well, if it's systematically front focusing, then at least the direction of adjustment (+ Backward) is obvious.

Can you please advise on other methods on dealing with front focusing and to get it spot on.

Here's a suggestion.

1. Find a distance at which you can achieve obvious moiré effects.

2. Use AF to achieve focus.

3. Using Life View, and assuming sub-optimal focus (otherwise quit ;-) ), note

*in which direction* you need to manually adjust focus to maximize moiré.

4. Depending on the amount of adjustment needed, choose an adjustment

*amount* and adjust in the direction to compensate for the

*direction* of adjustment needed as determined in step 3.

5. go back to step 2. and do another iteration.

The amount of adjustment for each iteration depends on the total amount of adjustment needed. The theoretically fastest way to hone in on the optimal setting, is a binary one. Given you've already determined in which direction you need to adjust (in step 3.), over-adjust the maximum amount possible from your starting position. Then for each next iteration use half the amount to adjust in the opposite direction of the previous iteration.

Assuming one starts from a 0 adjustment setting, and a front focusing lens (requiring a positive adjustment direction to move the focus plane to the back), one could use +20 for the first iteration. This will probably over-correct to an AF backfocus situation. Then use an amount of -10 from the +20 starting point, so you'll use +10 for the next iteration. It then depends on which direction you need to correct manually, whether to use +/-5 (5 or 15) for the next iteration, use +/- 2 or 3 for the next, and +/- 1 for the final. When you over-correct then switch direction, otherwise use the same direction, but with half the amount of difference of the previous iteration.

The more difficult task is one of concentration, to choose the correct direction for the next iteration. Just remember, if you consistently need to manually correct towards a farther focus plane then use a more positive adjustment value, and obviously a more negative value if you need to manually focus nearer by than AF achieves.

Also don't forget to verify the settings you've found at different distances and when starting from either minimum or maximum focus starting position.

Bart