Which shutter speed handheld ?

[yb98]

I have read somewhere that to avoid blurring in a handheld shot, the shutter speed depends on the focal length. For instance, for a 50 mm focal length, the shutter speed must be lower or egal to 1/50 s.
For 100 mm, 1/100 s and so.

Is this true or is there any rule to calculate the shutter speed to avoid hand movements blurring ?

Also should we take into account the 1.6 crop factor of the DRebel. For instance with a 50mm length, must the shutter speed be lower than 1/50*1.6= 1/80 s

Yacine.

[scottbergerphoto]

You are correct. The minimum shutter speed for handheld shooting is 1/focal lenth. You should also figure in the crop factor because the crop maginies any movement. So for a 50mm lens and 1.6 crop factor, it would be equal or faster then 1/50x1.6 1/80 (1/100).
Scott

[Pekka]

Note that 1/focal rule applies to small prints only, and to subjects that do not move. If you print larger you will need more speed. If you move or/and your subject is moving you will need more speed, and even more if the moving subject is closer.

Good thumb of rule is: if you intend to stop movement and camera shake use as fast shutter speed you can get. Do not be afraid of high ISO to achieve this.

[Jesper]

Note that the 1/focal length rule is not a law, it's only a rule of thumb. It won't guarantee that your photos are going to be sharp if you follow it, nor does it mean that it's impossible to make sharp photos if you break it.

If you have a lens with IS (Image Stabilizer), you can use shutter speeds that are much slower than the 1/focal length rule suggests and still have a good chance of getting sharp photos.

You should take the 1.6 factor in account, because you're enlarging the image 1.6 times more with a camera that has the 1.6 factor. Also, Pekka is ofcourse also right about the fact that the rule is valid only for small prints.