Originally posted by crossover37 I was taking some portraits last night of my brother-in-law with my Sigma 50-150mm f2.8 and the shoot was going well but when I had the sun behind him or a little to his right the lens wouldn't lock focus correctly. It would lock but it wasn't locked on him, he was blurry. This happened like 10 times, I had to manual focus sometimes but that is just as bad because I can't tell if he's sharp (he was around 20 feet away and I was at 70mm zoom). Anyone experience this with their Sigma 50-150mm f2.8?
Hi there! I too have the same lens and have no problems shooting under similar conditions as how you were shooting. Here are some shots indoor but against strong lights which were taken at a FL around 70mm, aperture of f2.8 and ISO800 with my K200D:
May I suggest that you do the following in sequence:
1) remove the lens from the body and then reinstall it;
2) focus on a close subject at different focal lengths to check if focusing is aligned;
3) focus on a distant subject subject at different focal lengths, then if focusing is correct;
4) focus on a subject which is backlit.
If the problem occurs again, well you may need to send in the lens for a check up.
Hope this helps.