Archived posting to the Leica Users Group, 2004/02/16
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
From http://www.minoxlab.com/Don_Krehbiel/mpl/dkdof.htm
"Depth of Field is the total distance, on either side of the point of
focus, which, when viewed from an appropriate distance, APPEARS sharp in
the final print."
"A lens focuses at precisely ONE distance. Everything on either side of
that distance is out of focus, PERIOD!"
"Points more distant than the plane of focus are resolved as points in
front of the film, becoming fuzzy circles by the time they reach the
film."
"Points closer to the camera would be resolved as points behind the
film, so they are also fuzzy circles when they reach the film."
"If the size of the opening is reduced, narrowing the light passage, the
size of the CIRCLES OF CONFUSION are reduced on the negative. Thus,
"stopping down" or making the aperture smaller gives smaller circles of
confusion and extends the range of apparent sharpness. Enlarging the
negative enlarges the circles of confusion, hence even smaller apertures
are required as the enlargement factor increases. Remember we are
striving for 1/100th inch on the print!"
From http://www.outsight.com/hyperfocal.html#dof
"Without going into the physics involved, this apparent depth of field
is due to a phenomena called circle of least confusion. When an object
is at the exact distance the lens is focused, every point on the object
will focus to a point on the film plane. When an object moves out of
focus, on the film these points begin to grow and become circles. The
farther out of focus an object is, the larger these circles become. But
up to a certain point (again depending on film size, lens focal length,
etc.), these circles of confusion are unobtrusive and the image appears
to be in focus over a range of distances and has 'depth of field'."
Jim - http://www.hemenway.com
- --
To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html