Depth of Field (DoF) is not a simple measurement. The rules are simple, however. If the frame is filled with the same subject, then the DoF will be greater at smaller focal lengths. This is the reason my Coolpix 8700 has higher DoF than my Digital SLR for the same image. Focal length multipliers do not apply to DoF. Light diffraction effects start to degrade the image in smaller cameras faster than in SLRs, so that this effect is effectively negated. For example, my Coolpix 8700 is diffraction limited at f/4.4 and my digital SLR at f/13. Thus, maximum DoF while retaining maximum sharpness is attained at those apertures.
-- Ram-Man 12:38, 14 June 2007 (UTC)