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Re: COCs

  • From: Stephen Kearney <slk@xxxxxxxxxxxxxxxx>
  • Subject: Re: COCs
  • Date: Fri, 02 Oct 1998 10:56:04 -0700
Regarding DOF, focal length (FL), and MF/LF, I think the important concept to
remember is that an f-stop is not a constant value.  It's a ratio of the FL.  But
as Ben Weiner said it's the actual diameter of the aperture that determines DOF.
The same aperture diameter on a 50mm lens might be f/8, while on a 100mm lens it
will be f/16.  So to get the same DOF you have to have to stop down 'more' on the
100mm lens.  And since a 100mm lens gives you the same angle of view in MF as 50mm
lens in 35mm (approx.), you have to stop down 'more' in MF to get the same DOF.

-Stephen
  • References:
    • COCs
      • From: Greg Erker