tammy autofocus issue at concert

[pregnantcowlady]

does anyone with a 17-50 have an autofocus issue in really low red ambient light?
i've never had this issue before until last night when i was shooting a show and i couldn't get a decent picture worth a darn.

it's a pretty sharp lens and i've never had this problem, i was at a wide enough aperture to where it should have put both people in focus, but it was hunting and picking and choosing.

is the AF going bad? anyone else experience this problem?

here's an example. http://i16.photobucket.com/albums/b44/pregnantcowlady/mddathorizonschurch033.jpg

[narlus]

shutter speed = 1/10th.

that's the problem.

bump up yr ISO from 400 to at least 1600..that would still get you only 1/40 at the same metering...sometimes you need the speed of primes.

[René Damkot]

Motion blur.

On a side note: No matter what a DoF calculator might say, IMO you won't get both in focus at f/2.8.
You will be able to see the difference between "sharp" (focussed on) and "within DoF" (almost sharp)

[Jam71868]

additionally, and I don't know the technical reasons why, but red lights always cause problems. I usually have to adjust the white balance or take out the red using a filter in post processing. Red lights are tough.

[pregnantcowlady]

thanks guys.
i know i needed that prime at a time like this, i just have to save up for the sigma 30mm.
i guess i could have upped the ISO, but i am too afraid of noise.
next time i'll try that though, i just had a DUH moment. :)

and i hate red lights. why did someone invent them?

:(

[narlus]

PCL, don't worry about noise...i shoot @ 1600 on my 30D pretty much all the time...the 30D can produce a good image @ 1600 w/o any noise reduction.

[pregnantcowlady]

yeah, i will have to up it for next time, it will be a must.
thanks!!! :]