The Area that may be seen distinctly or resolved into a clear image . . . . A State or Condition permitting clear perception or understanding . . . . Emphasis . . . . A Point at which rays converge or from which they diverge or appear to diverge .
Adjustment is most critical when focusing on a nearby object with wide-open lens.
It is least critical for a distant object with the smallest lens opening. The accuracy of the focusing may be judged by observing the sharpness of the image on a translucent glass surface in reflect-type cameras or by superimposing two images in a rangefinder in some other cameras. The contents of this site, including all images and text, are for personal, educational, non-commercial use only.