That would depend on what type of image. For wide sweeping vistas then a low number is best. A "portrait" with a Poser figure near the camera needs a higher focal length (typically 80-120mm) to avoid distortion. Lower settings also exagerate the depth of objects in the scene where higher settings flatten the image. Another factor can be trying to position a camera inside a building. If you can't make a wall invisible so that you can move the camera back from the subject then lowering the focal length widens the field of view letting you fit more of the interior in. -- Mark

Mark