autofocus challenges

Joined: 05 Jul 2006 Posts: 13 Location: Melbourne

Hi there everyone - can I please have some advice.

I do a lot of ballroom dancing photography of my children. I use Canon 350D with the kit 75-300 telephoto. The conditions are obviously difficult - fast movement in poorly-lit environment - most of the time some distance away and needing the full range of the telephoto lens.

To be able to stop the action I use ISO800, with exposure in the 1/125 to 1/160th.

When I get the right "alignment of stars", the results I get are very decent. However, the rate of rejections is extremely high, as most shots end up being anywhere from a little soft to quite a bit out of focus.

The autofocus obviously is having a hard time coping with these conditions.

I've tried different autofocus settings, but still have not come up with a way to improve my success rate. The movement is too fast for me to be able to effectively use manual focus.

Does anyone have any pearls of wisdom to experiment with? Is this an issue with my hardware? Would using more expensive lenses for example produce more precise focussing?

Many tnx in anticipation.

Joined: 01 Oct 2005 Posts: 183

Well, you're working with a difficult situation. Low light makes it tough for autofocus to nail it spot on, not to mention that your shutter speeds are also a bit slow for a long lens coupled with motion (a minimum of 1/500 would greatly help to freeze motion). With what you've got, you're probably getting the best you can get. To improve your keeper rate in a situation like this, faster glass would be your best bet. Faster glass would give you a brighter viewfinder and improve autofocus plus it would give you faster shutter speeds.

Joined: 26 Jan 2005 Posts: 55 Location: Illinois, USA

I agree with jra, faster glass is the answer here. I'd recommend the Canon EF 70-200mm f/2.8 lens. Not as much reach what you are using but from 200mm prices start to increase dramatically.

I shoot the non IS version of this lens and can hand hold it with few problems. A monopod might help some or consider the more expensive version that does have IS.

Joined: 14 Feb 2006 Posts: 214 Location: Corona, CA

Two things. Faster glass and the Canon 40D. The 40D can supposedly go up to 1600 ISO and still look decent. In fact it goes to 3200 but it looks funky on that setting.