I have completed a few days worth of testing cameras and lenses with FoCal. I have the Pro version, and I'm running it on a 17" MacBook Pro (Core i5, 8 GB RAM) with the software installed on a Parallels virtual machine running XP SP3, allocated one physical core (2 virtual cores) and 3 GB of RAM. Most of the testing was with v1.1, although the first day was done with v1.0 (v1.1 was released the afternoon of the first day I spent running tests).
My overall impression is very good, with a couple of caveats. The software is easy to use, although there were several random crashes. There are still a few bugs in the software, for example, it sometimes reports that the current adjustment is optimal, when looking at the detailed analysis data shows that a different one is best (supposed to be fixed in the next release). Also, the Zoom view during target setup is based on the last location of Live View AF (i.e. from the last time you use it before lauching FoCal), so for that feature to be useful you need to launch Live View and center the AF rectangle.
As mentioned above while the testing was very straightforward with f/2.8 lenses and an f/4 lens, faster lenses gave it some trouble, sometimes resulting in a 'inconsistent results obtained so far' message (although allowing it to continue anyway often generated an excellent curve fit). This happened more often with the 5DII than with the 7D.
Setup was straightforward - the target search tool did a good job with most lenses/distances that I tested, although sometimes not, particularly with longer lenses at longer distances with the 5DII. The time taken for a test run was very short - even increasing the mirror lockup to 2 s (default is 1 s), test runs took less than 3 minutes. My setup consisted of the target taped to a wall, lit by three 150 W-equivalent gooseneck lamps pointed at the target from about 2' distance. The FoCal documentation recommends at least 10 EV, although it states that down to 5 EV will work; my lighting setup gave between 11 and 13 EV depending on lens and distance. Camera on tripod, with hotshoe bubble level to square it to the wall and a tape measure on the floor.
Comparing the results to what I obtained manually using the LensAlign Pro for the same lens/focal length/distance, the results were very similar - spot on for fast primes, and within 1-2 units for slower zooms (where there are usually a couple of values that yield good results due to the deeper DoF). If I tested like I have with the LensAlign, the whole process would be much faster with FoCal. It takes me about 45 minutes to calibrate a lens manually (one distance/focal length, 30 minutes for setup, image capture, and tear down, and 15 minutes for comparisons); the same process with FoCal would probably take less than 10 minutes.
The advantage of FoCal is that it simplifies the procedure to the point where it's simple to test multiple distances and for a zoom lens, multiple focal lengths. Any particular adjustment you make is applicable for that focal length and that distance, and may not be optimal at other distances or zoom settings. With the exception of the 1D X, we're limited to applying a single adjustment value per lens - that means making the best compromise. The more data you have to help judge the best compromise, the better.
I tested at 50x the focal length (recommended by Canon and FoCal), 25x the focal length (recommended by LensAlign), and for the 100L Macro, I also tested near the MFD using the small focus target. Without moving furniture around, the longest line-of-sight inside my house is ~35 feet, so I didn't test anything longer than 200mm (for which I'd set up outside, but daytime temps have been below freezing, and during the initial tests last weekend they were down in the single digits °F). For zoom lenses, I chose focal lengths loosely based on the zoom ratio, e.g. 3 focal lengths for a 2-3x zoom and 4 focal lengths for a 4x zoom.
Attached below are tabulated results for several lenses on the 5DII and 7D. Several observations occurred to me when looking over the data. First, distance matters - in some cases, testing at 25x vs 50x makes up to a 7-unit difference in the optimal AFMA, which is nearly a full depth of focus for the lens at max aperture, i.e. will be easily noticeable in real-world shots. For zoom lenses, different focal lengths give different results, and the progression is not necessarily linear nor unidirectional for a given lens (so, I wonder again how the 1D X will handle the two values for a zoom).
On the 7D, 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), the same lens on the 7D has 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 fitted 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.
Other notable findings not evident from the data were that the testing was quite consistent. Borrowing concepts for assay validation from work, I checked intra-run and inter-run variability, and both were quite low - repeating the same same lens/focal length/distance several times in succession yielded the same value (±1 for f/2.8-f/4 lenses), and re-testing after tear down and re-setup the next day yielded the same results. One exception was testing the 100L near the MFD, which gave more variable results; not a real problem since I almost always manually focus for macro anyway.
One other interesting observation concerned the target itself - for the first lens I tested, I decided to repeat the LensAlign manual method on the spot for a direct comparison to FoCal. After the manual test, on a lark I connected the camera to my Mac and ran FoCal with the camera pointed at the LensAlign. FoCal reported the same adjustment as it had with that lens using the printed FoCal target (which was the same as the manual value, too). Finally, the developer is quite responsive - good support is a critical part of new software!
In selecting an AFMA, I considered both the results at the different distances in terms of DoF for a given focal length, and also the distances which I commonly shoot for those lenses. For example, the value I chose for the 35L is biased toward the closer distance, since that's where DoF will be thinner; I picked the value for the 85L (even though there wasn't much difference) based on the fact that I usually shoot that lens at about 7-8 feet for portraits, which is ~25x the focal length. For lenses like the 70-200 II, which I shoot at varying focal lengths and distances, I selected values biased toward the long end of the zoom range, since that's where DoF will generally be thinnest and focus most critical.
