Which focal length is best for hand-held insect photography?
I’ve already talked about the advantage of keeping your distance from your subject, so you might think that a long focal length lens is better. However, this is only partly correct and a compromise is often needed. Depth of field (the amount either side of the plane of focus that is acceptably sharp) is greatly reduced when taking close-ups, so to obtain a photograph of good technical quality; you usually need a fairly small aperture, such as F11 or F16. This is bad news because it reduces your shutter speed, and you need all the speed you can get if you’re hand-holding a camera with a long focal length lens! If you take the ‘one over focal length’ rule as a starting point; for a conventional (i.e. non VR) 100mm macro lens used on a crop sensor (DX) camera, that translates to a minimum shutter speed of 1/150 second if you want to avoid hand shake. Because of the very close working distances, any camera shake or movement tends to be exaggerated, so 1/150 is actually a bit optimistic and
