In an effort to help others I have made a list of a few relevant points that I have found during my hours spent playing with micro adjust. Any further thoughts or contradictions are welcome.
This is not a thread to discuss how much MA each of your lens needed, there is already a thread for that.
Setup
Always carry out MA test and adjustment using normal AF through the viewfinder, Live View focus cannot be adjusted using MA.
Always use a stable tripod and a remote shutter release. Likewise ensure that target is also fixed in position and cannot move during the tests.
Lighting
Fluorescent lighting can cause errors, as can power saver bulbs. An incandescent (filament) bulb seems to work but the best results are obtained in daylight.
Target
Do not use batteries or toothpicks, batteries have rounded surfaces which complicate things and toothpicks are too small. Do not use a sloping or angled target, use a large flat large target which covers twice the area of the focus point,remember that the focus point shown on the screen in your camera is not precise and in reality the focus area may extend slightly around that point.
You can put an angled ruler in the frame but out of the field of the focus target. The target should be as parallel as possible to the cameras sensor.
I have found that a multi-coloured target such as a coloured print on matt paper works much more reliably than something that just has black and white patterns.
Distance
Canon state 50x the focal length, others say 25x. I have found that if you adjust to 25 times then you will more than likely have errors at greater distances.
Using just the centre focus point test at 50x, then repeat the test at 100x (which is why you need a large taget). You may have to compromise on your MA settings to get the best at both distances. Finally I carry out an infinity test on a very distant subject.
You will need to make at least 3 shots at each setting, taking the lens off focus manually between each shot, then pick the most consistently focussed shots to decide on any MA that is needed.
Lenses
Prime lenses are usually straightforward apart from the distance compromise noted above.
Zoom lenses can be a nightmare, You will almost certainly have to settle at a compromise to suit both ends of the zoom plus the distance compromise noted above. It also pays to check at various settings within the zoom range because any deficiency may not be constant throughout the entire range of focal lengths.
Results
Do not expect perfection, you will not get it.
Do not expect a wide aperture lens to hit focus down to the millimeter on every shot because the AF system doesn't work like that, it is only designed to get within one third of the depth of field. If Canon made it work to finer tolerances then we would probably all complain how slow it was.
Finally
Once you have your settings in the camera forget all about MA and go out and get some pictures, after all that is what you bought all that gear for. Don't constantly pixel peep thinking that you need further adjustments because as I've already said " You are not going to get it perfect"
