At first sight, using a zoom lens is simplicity itself, for all you have to do is to adjust it until you have the right shot, then focus up. But there is much more to it than that! A zoom lens behaves differently throughout its range.
Long focal length / narrow-angle setting —
As we saw earlier, when the zoom lens is ‘zoomed in’ towards its telephoto limit it has certain frustrating features:
• It is difficult to hold the shot still (camera shake, unsteady framing).
• Depth of field can be shallow; subjects easily move out of the focused zone.
• Focusing can be very critical; it may be hard to judge what is in focus.
• Slight focus control adjustments can produce considerable changes.
• Perspective appears compressed. ...