What is the Depth of Field of my lens if I know my Focal Length & Film Format Size?
Depth of Field is is the distance between the nearest and farthest points in the object field that appear acceptably sharp in the photograph. Depth of field varies with lens aperture, focal length, camera-to-subject distance, film format, print (or image) size and the distance from which that image is viewed. By definition, depth of field is dependent upon the viewer’s perception of “acceptably sharp”. If you make larger prints, or view them from a closer distance, depth of field is reduced. Make smaller prints, viewed from a distance, and DOF increases. There are standard values for the acceptable blur circle of a point that can be used to DOF. Those values will provide useful DOF information, except in extreme circumstances (like VERY large prints). We’ve made a DOF Calculation spreadsheet (requires Excel), using the standard blur circle values, that you can download here.
