critical_focus_test

[Stephen Locke]

I've been running more tests to see how lenses perform in difficult situations. In particular I'm interested in knowing when and how the auto-focus fails in low light or low contrast situations. Skies/horizon lines often have mushy contrast especially toward sundown. This test was with bright hazy light right before sunset (shooting east). No foreground obstructions. I fired off 32 exposures. 13 (40%) were sharp. 19 were slightly soft or just plain out of focus. Canon 24mm f2.0 1/200. 100% enlargement.

If I want to be sure the lens is properly focused on infinity I will have to put it there manually.