John, nice work on the software testing. Im curious, did you zero the AFMA between runs on each lens or did you just leave the previous settings from one run to another?
John, nice work on the software testing. Im curious, did you zero the AFMA between runs on each lens or did you just leave the previous settings from one run to another?
Bob
Hi Bob,
I tried both without and with zeroing in between runs and it didn't seem to make any difference. FWIW, I did much of my repeatability testing with the 24-105mm f/4 IS, since that's the lens I use most on the 5DII. Generally, though, the f/2.8 lenses gave the most consistent results (and had the tightest point spreads with a steeper curve.
Did you check the analysis info after each run? That avoids the known bug of it reporting no change needed when, in fact, a different value is optimal.
BTW, working on short lenses on the 7D now. Preliminarily, testing distance and especially focal length for zooms seems to have a much larger impact than on the 5DII - the spreads seem bigger. I'll try to post the data tomorrow.
Nope, But I plan to run my other lenses through the test again this coming weekend and I will watch the analysis info this time.Did you check the analysis info after each run? That avoids the known bug of it reporting no change needed when, in fact, a different value is optimal.
Bob
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
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
FWIW, here are the results from a few more lenses tested on the 7D:
Lens Focal length 50x AFMA 25x AFMA Selected AFMA EF 70-200mm f/2.8L IS II USM 70mm 5 4 2 135mm 1 3 200mm 1 2 EF 85mm f/1.2L II USM 85mm 1 -2 -1 EF 100mm f/2.8L Macro IS USM 100mm 2 3 2 ~MFD: 0 or 4 (n=2) EF 135mm f/2L USM 135mm 5 1 3
This just leaves the 100-400mm and the 70-200mm with 1.4x and 2x TCs, holding off until it's a bit warmer outside...
The sorts of data which can now be collected are making even the two-point AFMA on the 1D-X seem needlessly primitive. With the right software one can get a whole heap of AFMA data in, what, maybe an hour per lens--body combination? Distilling this down to one pair of AFMA values (or worse, a single AFMA value) is then in a needless compromise, especially given it's only a software issue. I agree with John's observation that the correction is non-linear. My preference would be to be able to provide to the camera exactly the sort of grids being posted in this thread -- the AFMA given a focal length and distance-to-subject -- and have it extrapolate between points.
(The cynic in me wonders if the AFMA feature is deliberately crippled. At the risk of opening a can of worms, third-party lenses seem to need more correction, so a comprehensive AFMA mechanism would allow any deficiences to be compensated for. Or, even with Canon lenses, if they calibrate them after the warranty period, they pocket a nice fee.)
Like many others in this thread I have been contemplaating the calibration of my 7D and 5D MKII to my 6 Canon lenses. While both LensAlign and SpyderLensCal have performed well for many people I was hoping that there might be something better on the horizon. Once again I wrote to Bryan and, once again, he had a great suggestion... FoCal... and this thread.
Have read the theory of FoCal until my eyes glazed over and have found the information on the site and in this thread very illuminating. One question I did have came to mind when I read the posting from John relative to doing a calibration with a 1.4X TC attached to his 70/200. I am going to both admit and show my ignorance by asking how, exactly, would the camera AFMA go about identifying a lens with a TC on it and how would it be listed/registered within the index of AFMA lens in the camera?
I have long thought that both my 100-400 and 70/200 have been a bit soft with the TC (and the 100-400 by itself). FoCal may just be woth its weight in gold to a "non-techie" "sort-of techie" like myself. Thanks for any help or suggestions any of you may make.
Bill
The camera knows you have the TC on, as long as it is a Canon TC.Originally Posted by Bill_in_WA
I always thought the same when using the TC with zoom lenses that the TC was to "soft". The 70-200mm II might be close to performing acceptable with the TC on but I have never had a need for it, really I have only found the 1.4x acceptable on the super telephotos and primes. Really it all depends on what you think is "acceptable" and my opinion may not match others.
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