Focusing with sunset

[sinus007]

Hi,
Last night I was taking pictures of friends & family at a beach with sunset on the background and observed interesting and dissapointing thing. When the sun was at about 10 deg or less my autofocus went haywire: first camera focused on the subject very fast, as usual, and then focus drifted off as if somebody was moving the focusing ring and stayed out of focus.
Unfortunately I didn't have time to experiment. First I tried to adjust manually with the quick shift, but the focus drifted anyway. Then I switched to manual and it worked fine. Being afraid that something happened with the lens I turned away from the sun and tried to focus - no problem. Turned back to sun - problem reappeared. Oops, forgot to mentioned - I was using k200d and da*16-50 and was using AF Select setting.
Any ideas?
Thank you very much.

[IsaacEastgate]

i've experienced this. The AF sensors are sensitive to sun flare, which ruins contrast so there is nothing to detect. Find something the right distance away to focus on, or put your hand covering the sun, and dont ever use AF continuous unless you are birdwatching

[sinus007]

Hi Isaac,
Why is that?

Originally Posted by IsaacEastgate

and dont ever use AF continuous unless you are birdwatching

Thanks

[Marc Sabatella]

Originally Posted by sinus007

Hi Isaac,
Why is that?

Well, that might have been a slight overstatement, but clearly, AF-C is intended for subjects that are actually moving, so it can keep them in focus as they move. If the subjects are standing still, then using AF-C is just inviting the camera to refocus for no reason. Use AF-S, so once the camera has focused, it stops trying to focus again and again and again.

[sinus007]

Thanks a lot.