Reikan FoCal - Automatic AF Micro adjustment software

[neuroanatomist]

Here are the results from some shorter lenses on the 7D:

Lens	Focal length	50x AFMA	25x AFMA	Selected AFMA
EF 16-35mm f/2.8L II USM	16mm	3	-4	4
	24mm	8	2
	35mm	6	7
EF-S 17-55mm f/2.8 IS USM	17mm	-5	-2	2
	35mm	0	5
	55mm	0	4
EF 24-105mm f/4L IS USM	24mm	1	-1	2
	50mm	2	1
	85mm	3	2
	105mm	2	4
EF 35mm f/1.4L USM	35mm	5	-2	0

The wider zooms seem to have much more spearation between values based on focal length and distance, e.g. comparing the 16-35mm II on the 5DII with a 5-unit gap (-5 at 16mm 50x to 0 at 35mm 25x) vs. the same lens on the 7D with an 11-unit gap (-4 at 16mm 25x to +7 at 35mm 25x). Likewise, the 35mm prime shows a larger differential from testing distance (5 units on the 5DII, 7 units on the 7D). I wonder if this is due to the thinner DoF with the 7D (the distances are the same as with the 5DII, so the shot/framing is different, but under those conditions the APS-C sensor delivers shallower DoF). In general, the curves for the same lenses were steeper on the 7D than on the 5DII, analagous to the difference bewteen a slower and a faster lens.

Not sure how useful these results will be for me...most of my shooting in the shorter ranges is with the 5DII, on the 7D I do use the 17-55mm but not really the other lenses, more the 100-400mm and sometimes the 70-200mm. I think this was the second time I've mounted the 35L on the 7D, and the first time was for the LensAlign AFMA... Still, I wanted to test the same lenses to get an idea of differential performance across bodies. Also, the 7D can certainly be a backup camera to the 5DII, so if I need to grab it and shoot, I want the adjustments ready.

Might get to the 85L, 135L, and 70-200mm II on the 7D this evening.

--John

[HDNitehawk]

John

Taking a look at your results, it is no wonder people have trouble doing this with cereal boxes and yard sticks.
I would have a problem just picking what number to use as an average.

Looking at your results with the 5D II and the 70-200mm they are similar to the results that I was seeing with the lensalign. If you were to graph the AF performance in relation to the lens length, initially to me it seems the lens has an elongated S curve the optimum AF point follows. The designers of the lens obviously know this. I wonder what point on the lens did they use to determine what point would be the zero point for optimum AF performance. Say if they use the point where the lens is extended to 145mm it would give the best average for the lens throughout. It would be nice to have this information, maybe if someone were to ask nicely Canon would tell us the best point to establish an AF adjustment point is at XXXmm......probably not....

Rick