FOCAL LENGTH & HANDHELD PHOTOS

FOCAL LENGTH & HANDHELD PHOTOS

The focal length of a lens may also have a significant impact on how easy it is to achieve a sharp handheld photograph. Longer focal lengths require shorter exposure times to minimize burring caused by shaky hands. Think of this as if one were trying to hold a laser pointer steady; when shining this pointer at a nearby object its bright spot ordinarily jumps around less than for objects further away.

This is primarily because slight rotational vibrations are magnified greatly with distance, whereas if only up and down or side to side vibrations were present, the laser's bright spot would not change with distance.
A common rule of thumb for estimating how fast the exposure needs to be for a given focal length is the one over focal length rule. This states that for a 35 mm camera, the exposure time needs to be at least as fast as one over the focal length in seconds. In other words, when using a 200 mm focal length on a 35 mm camera, the exposure time needs to be at least 1/200 seconds-- otherwise blurring may be hard to avoid. Keep in mind that this rule is just for rough guidance; some may be able to hand hold a shot for much longer or shorter times than this rule estimates. For users of digital cameras with cropped sensors, one needs to convert into a 35 mm equivalent focal length.