Zoom and shutter speed

[singleguy]

Ok i read somewhere , as a rule of thumb, that in order to shoot fast enough to stop or freeze motion, that your shutter speed needs to be at least 1.5 x the focal length, or something like that. My new camera has a focal length of 5mm to 90 mm or 28mm to 504mm (35 mm equivilant), so is that rule of thumb correct, and if so, do i base my shutter speed calculation on the 90 mm length or the 504mm length?

[RichardTaylor]

The guide is not to freeze motion. It is to stop the effects of camera shake.
Freezing motion is very much subject dependant and the distance you are from that subject.

For your camera, without any aids like image stabilisation, I wouldn't shoot much below 1/30 at the wide end and 1/500 at the long end. It is an individual thing, depending on how steady the photographer can hold the camera so why not try some experiments yourself at the wide, midrange and tele ends of your lens and changing the shutter speed, then you will know for yourself when shooting. Try it with image stabilisation on and try it without.

[OsmosisStudios]

The rule of thumb is actually 1/focal length for 35mm equivalency. So in your cases 1/28 and 1/504, which is actually 1/30 or 1/500 as RIchard has said.