I had early success using FoCal fully-automatic mode to determine the micro-adjustment for my shorter focal length lenses. So far, I haven't been able to repeat that success with my super telephoto lenses. I did have success using the semi-automatic mode. I'm still pleased with the product - I'm writing this so that you can learn from my mistakes.
The root cause of my problems was that my rock solid tripod wasn't rock solid. The super telephotos magnify any motion and the motion destroys sharpness. While you cannot use IS during the test, this problem did demonstrate how dependent I've been on image stabilization.
I made my tests at less than the 50 times the focal length recommended by Canon. FoCal noticed this and told me to move to the correct distance. I didn't because I didn't have a place to do the test that was that long.
The motion made it difficult to center my camera on the target. FoCal shows a highly magnified shot of the target as provided by live view. The center of the view finder didn't perfectly match the center of live view. The image provided by FoCal on the monitor was slightly delayed. Any adjustment I made would bounce around because of my unstable tripod before finally settling down.
The FoCal semi-automatic mode then allowed me to focus, compare small focus changes, and make micro adjustment changes without actually moving the mirror or shutter. As a result, I was able to correctly adjust my camera and lens combination.
In real life, my tripod doesn't need to be as stable since I will be using IS and shorter shutter speeds. Still, my photos are only as sharp as allowed by the weakest link in my system so I'm more aware of the need for a stable tripod. Instead of shooting at ISO 100, I may move up to 320 for higher. I'll also use mirror lock-up when it is practical.
I've noticed some online complaints from individuals who haven't used FoCal. They are worried about FoCal requiring the serial number of their cameras. They imply that their privacy is somewhat compromised. Privacy isn't the problem - the real problem is piracy. When I started to research FoCal I found a number of places where the code could be downloaded for free. The serial number is used as part of the software encryption. Stolen code will not work without a camera with the correct serial number. If you can afford the cameras and lenses you are testing, the value added by FoCal is definitely worth the purchase price.
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