Flash Photography and using a Zoom lens

[MKJ]

I am new to DSLR cameras. I recently purchased Canon's 30D, seems like a real good camera. Of course I am not to familar with all of the competors. The last camera I purchased was the New CanonF1, which I still have and it runs great. To my question, can you use a digital camera such as the 30D with a flash (either one attached/separate from the camera) with a zoom lens? If so what would be the largest zoom lens you could use with a flash? I assume a flash that is separate from the camera is more powerful. Using a flash with a zoom what would be the maximum distance from the camera to the subject be? Would I be better off purchasing a zoom lens with Canon's IS feature. I will be photographing the World Cup finals in Dressage at the Mack Center in LasVegas. I am not sure what the lighting will be like and want to be prepared. Any information about the above would be appreciated

Thanks

[cwphoto]

Working distance is related to the GN, the flash's zoom, the working ISO, and the f-stop set.

I'd say go for a 580EX which would give you a working distance of 80m at ISO 1600 using f/2.8 should you need it.

A flash will work with any lens (except some ultrawides).

[MKJ]

What do think about the Canon 70mm-200mm F2.8 IS. Is this lens compatible with a flash? With the IS I probably would not need a flash. I have no experience with IS Canon lenses, I have heard a lot of positive comment about them. Would this zoom lens work inside a convention center, filming horses that move at the canter and trot (movement is not to quick)

TY

[cwphoto]

Yes, as I said before, every lens bar the superwides.

If there is sufficient lighting in the convention centre then that choice of lens sounds good to me. IS will help you get sharp shots of static (or near static) subjects without a tripod, but is generally useless when there is significant movement in the subject.

I would still take the flash for this task and try some with/some without.