kenthilburn wrote:Wow. I knew it would tough, but not that tough. Thanks for the help. I was leaning toward the IS anyway.
The full F-stop table is,
F1.0, F1.4, F2.0, F2.8, F4.0, F5.6, F8, F11, F16, F22, F32
Each halving or doubling of aperture has an inverse affect on shutter speed, as does ISO
As an example if you were getting a shutter speed of 1/500th at ISO200 at F5.6, going to F8 would effectively halve the shutter speed to 1/250th, f11 would become 1/125th and so on, so to get 1/500th at F8 back you would double the ISO to ISO400, or F11 at ISO800 and so on. The poorer the light is the more you need to consider a fast lens and/or high ISO hence Dougj suggesting a minimum of F2.8 and for sports I would assume most would recommend a 70-200 F2.8 and a fat pocket, assuming you can get close enough to the action!!! With IS you're potentially adding scope to achieve an extra 3-4 stops, so what you could manage at F5.6 without IS you could potentially get away with the same shutter speed at F16, or what you could manage at ISO800 without IS you could potentially get away with ISO100 with IS etc. Remember, IS improves the results hand held and at slower shutter speeds but doesn't mean you'll get the shutter speeds you need for some situations. You may get a crisp results at 1/30th but if the subject needs to to be stopped at 1/300th for a clear shot you'll be back to needing a fast lens or high ISO to get the shutter speed.
Below is an attempt at some rodeo shots. It was reasonably bright (some moving cloud) but I still had to use ISO to get the shutter speed to stop some of the action. With the benefit of hindsight maybe ISO800 would have been better or at IS0800 I would have had the scope to use F8 or F11.
http://www.pbase.com/djwixx/8seconds