Advice on shooting personal trainers... in gym

I may have a project coming up that involves photographing some personal trainers going about their business.

The shots would be in a gym, with minimal natural lighting.

I will be using my Canon 40D and the kit lens 17-85mm f/4-5.6. I also have a 430 EX II.

The question is should I be using the flash? Should I go for shots without? Is this lens going to give me desired results... such as reportage style, candid shots of the trainers instructing their clients...

Any thoughts or advice on what I should and shouldn't be doing would be greatly appreciated...

Thanks in advance

D

I would want a faster lens. Try some shots with flash and some without. By all means BOUNCE that flash, you don't want harsh shadows everywhere. Go for some natural shots but don't be afraid to pose something you think might look good. You could also suggest moving some activities near a window for more light. Good luck!

The best result will come if you can combine the flash with existing light. You might want to place a orange gel over the flash for best light balance. Bounce the flash as mentioned unless you have some sort of nylon fabric or an umbrella you can fire it through. You should be able to get Ok results with what you've got. You might have to increase the ISO a bit to 400 or 640 if the ambient light is not good.