« on: October 08, 2014, 08:03:01 AM »
Actually, one thing worth mentioning is that FoCal does let you know when your gear is not operating properly. You will get errors during the test, or you will get a completed test that rather than showing a nice bell curve of IQ throughout the AFMA range it will look like buck shot scatter. When this type of thing happens you know you have something wrong with your gear that no AFMA setting will cure.
While this is rare, it has happened to me before. I had a 300 f2.8IS that worked perfectly for a couple of years. (I originally and successfully calibrated it with FoCal when I bought it). I then had a suspicion that I was having some problems. Not as many images were achieving the tack sharp focus I had enjoyed. So, I ran it on FoCal and got testing consistency errors along with huge variability across the AFMA range. I sent the lens in to canon and they had to replace an IS motor. FoCal confirmed it for me.
Another instance was with my 5DIII. I have two of these bodies, and immediately when I purchased them I ran them through FoCal with my lenses. Originally they were within about 5% of IQ of each other at optimal AFMA on any given lens. After over a year I began to suspect that one of the bodies was having some trouble. Totally gut instinct... it wasn't like one just stopped working. So, again I ran both bodies through FoCal and sure enough, the body had a problem. Instead of being within 5% of each other, there was over 30% IQ loss on the body in question. I sent it in to canon and they "fixed" it. When I got it back, I ran the test again, and Canon had done absolutely nothing to fix the actual problem. So I sent it back, this time with all the FoCal printouts. A few days later my camera came back with some hardware work and it was fixed.
FoCal is an excellent tool for calibrating AFMA, but it is also an excellent tool at helping to diagnose when there are problems with your gear. Is it worth $150 to me? At least....