Originally posted by Marc Sabatella I disagree. The moral is, be careful how you test. Real world test subjects very often lead people to be seriously mislead, as the camera might be simply choosing a different focus poin. AF test charts are designed to reduce/eliminate that possibility, but it's still possible to use them incorrectly. And they do have the disadvantage that they can usually only be used from close focus distance. But the lessons you learn from using AF test charts is essential if you want to perform a test using real world subjects that isn't completely invalidated by the camera choosing a different target than you intended. And this sort of experience also carries over in focusing in the real world for real - eg, not just for tests.
Can't disagree with "be careful how you test"
I can understand when one is working in a carefully set up repair lab, that a close focused test chart can be very accurate. Too many tiimes, i've been reading "but be careful to keep the camera lens perpendicular to the test chart" which is starting to make me think that people have experienced problems with their setups. The first time i did a test chart and submitted it online, sure enough, i got the comment back that hadn't aligned it properly. Also, it seems like one might have a potential front focus problem of doing the focus test indoors with tungsten lighting, then going outdoors in sunlight to take real pictures (unless one has the K7 of course)
The problem is, that a small alignment errors up close can get magnified many times at normal image distances.
I was stopped on a highway for an extended time yesterday, and so took out my K20 with my latest ebay lens purchase, and did a auto focus on the window edge of the car in front of me, some 25' away. I did trial and error AF camera adjustment, plus and minus until i had something that was close based on my katzeye focus screen (done at f2.8). Finding a focus edge on a car is not the most appropriate arrangement, but i still wonder if at distance setups may not be more useful than these up close indoor focus tests.