P3D DOF and Hyperfocal distance - part II

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

  For a given focal length, the hyperfocal distance is only a function 
  of aperture.
  
  Here is a Table of Hyperfocal Distances for 35 mm lens and 1/750 in.
  (0.03 mm) circle of confusion (applies for most all stereo cameras):

  Aperture  HF (m)  HF (ft)
    f22      2.0     5.0
    f16      1.8     8
    f11      4.0    11
    f8       5.0    15
    f5.6     7.0    22
    f4.0    10.0    39
    f2.8    15.0    44

  When focusing at the hyperfocal distance, everything from half this
  distance (exactly half) to infinity will be sharp.  For example, at f8 
  if you focus at 5 meters then everything from 2.5 meters to infinity 
  will be sharp.

  If your camera has a built-in DOF scale then you can get this
  information by simply setting one aperture mark to infinity.
  The camera is then focused at the hyperfocal distance of this
  f-stop and the other aperture mark points to the close focusing
  distance (which is half the focusing distance).

  How to use this information?  We mentioned earlier that at f8
  aperture, if you focus at 10 feet then everything from 6 to 29
  feet will be "sufficiently sharp".  If your scene includes
  infinity then you should focus at the hyperfocal distance of f8 to
  get the maximum DOF.  This is 15 feet.  If you focus at 15 feet
  then everything from 7.5 feet to infinity will be in focus!

To be continued.... -- George Themelis



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