Pictures taken with a telephoto zoom lens are not as sharp as those taken with a shorter focal length lens. Why?
The decreased sharpness is most likely the result of small movements while holding the camera. As lens magnification increases, so does the effect of motion on a camera that’s handheld. For example, a picture taken with a wide-angle lens at a shutter speed of 1/60th will usually be sharp but will probably show some camera movement with a 300mm lens at that same shutter speed. A handy rule of thumb is to use a shutter speed no slower than the reciprocal of the lens focal length when the camera is handheld.
