ChrisA said:WHen you get past a 200mm lens you are talking about using a tripod. That 1/(lens focal lenght) rule will get you. At 400mm you are limited to shooting at 1/400 and faster unless you are using a tripod. and even 1/400 is slow if you want very sharp shots.
Get a tripod head with a quick release plate built into it. Then it will be easy.
The 1/(focal length) rule is based on the 35mm format.
So in order to have a "sharp" image at 200mm; one needs at least 1/200 shutter speed.
I agree in the digital format one might need a tripod or monopod for something past 200mm. But with IS/VR 200mm in digital (close to 300mm) is very doable. Anything above that might need some sort of support.
More to the point, if one had a 400mm lens on the more popular DSLRs; one would need at least 1/600 of a second shutter speed to match the capabilities of a 35mm camera at the same focal length.