Depth of Focus
Depth of Focus measures the displacement of film within a camera. Also known as “lens-to-film tolerance”, depth of focus is measured microscopically (in thousandths of an inch, for example). Although this term has been interchangeable with “depth of field” in the past, depth of focus refers to the image placement on film within the lens, rather than the distance of the object from the lens.
Like depth of field, depth of focus decreases with larger lens apertures, meaning that the image will appear larger on the resulting printed photograph.
Unlike depth of field, however, depth of focus decreases with a shorter focal length or with a subject that is further away (depth of field increases under these circumstances).
With a standard lens, the formula for depth of focus is:
(Focal length x F-stop setting) / 1000
Distortion Distortion refers to an abnormality in image or sound quality. In photography, image distortion can occur in a photograph for a number of different reasons, including (but not limited to) ...