So whatever works for you, fine! But do not tell me that my method doesn't work, and for me it works much better, because aiming in between very long and very short distance to subject I get sharp POF on ALL distances. I did so with these lenses: ef 14L II, 24 1,4LII, 50L, 85L (twice) 70-200 II, 300 f2,8 L IS. That's the way it was and always will be.
Agreed. I've gotten excellent results with the LensAlign Pro and a much longer list of lenses than yours, and it works for me. If your method works for you, keep doing it!
I won't quibble, but I will correct a few inaccuracies:
Adjusting at mfd will never be accurate enough. At Northernlight they suggest you use at LEAST 50 times the focal to adjust.
Once again, not MFD. The usual recommendation is 25-50x the focal length of the lens - frequently qualified by the advice to test at the most relevant/common subject distance for your typical subject(s). Granted, that's not always easy because most people shoot more than one type of subject with a given lens.
I have fiddled around with charts and moirÃ© patterins at 1m or 2m
The problem there is not the distance, it's the other part of the statement - fiddling around with charts and moirÃ© patterns. Printed charts don't cut it, and moirÃ© patterns have too much play (little to no discernable difference with a pretty large degree of axial movement) and problems with alignment. You need to use the right tool for the job. If your auto mechanic 'fiddled around' with a crescent wrench when working on your car's powertrain, instead of properly tightening the bolts with a torque wrench, you'd have maintenance issues down the line.
Your subsequent statement about the SpyderLensCal, "I tried it and it made sense of the adjustments I already had done,
" is totally consistent with what I'm saying here - when you use the right tool, you get accurate results.
First off, When you use 1dmkIV the focusing point is so large that it covers at least too much of those fine lines on a chart to be even remotley accurate.
With this and other, similar tools, you're not focusing on the ruler with the DoF scale - the ruler is at an angle to the vertical so the scale has depth, and your focus target is a larger square with a contrast scheme optimized to activate any AF sensor point geometry (horizontal- or vertical-line, cross-type, or diagonal cross-type) that is aligned to be parallel to the image plane (and thus orthogonal to the AF sensor).
The SpyderLensCal you linked to is constructed in the same way (but it seems to lack a feature to facilitate parallel alignment of the camera with the focusing target.
Rather, there are some points that I overlooked and that are very important....I'll repeat the procedure next week end...
One point that has not come up, but which is quite important, is what autofocus microadjustment really does. What AFMA does is correct for systematic error in the AF system, specific to manufacturing tolerances in cameras and lenses. It corrects for bias in the AF system, or put another way, it improves the accuracy of the AF system. The terms accuracy and precision are sometimes (improperly) used interchangeably - accuracy is 'closeness to true' whereas precision is repeatability. Here's a diagrammatic example:
AFMA corrects for accuracy but does nothing
for precision. Chuck Westfall has told me that, "The AF precision for the standard precision sensors is within the depth of focus for the maximum aperture of the lens, while the AF precision for the high precision sensors is within 1/2 or 1/3 the depth of focus for the maximum aperture of the lens, depending on the camera model under discussion.
" Note that depth of focus is measured at the image plane of the sensor, and is different from (but affected by the same parameters as) the depth of field. I interpret that to mean that although the precision is specified, for example with the f/2.8 sensor all the shots will be focused within a region that is 1/3 of the depth of focus deep for that lens' maximum aperture, focusing could still be inaccurate (i.e. it would look like case C above).
AFMA moves the center point - the 'average' focal plane of multiple measurements. But it's important to remember that precision plays a role, so if you test your AF system with just one or a couple of tries, random chance says your test won't be 'spot on' due to imprecision. So, when testing AF performance, you need to perform multiple tests for a given lens, and fewer tests would be needed for an f/2.8 or faster lens due to the higher precision. I suspect this is what's behind Canon's statement that AFMA can prevent correct focusing - if you base an adjustment on one or two test shots, and those shots were relatively far off the correct focal plane, then on average most of your subsequent shots will miss focus.
Bottom line - no camera will produce a perfectly focused image every time at every distance, period. No adjustment procedure will change that. What a proper AFMA can do is increase the percentage shots that are correctly focused.