P3D Re: To Focus or not to Focus?

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Dr. George A. Themelis wrote:

> Here is a Table of Hyperfocal Distances taken from Realist instructions:
> 
> Aperture  Focus at     DOF is from-to
> --------  --------  ------------------
>   2.8       44 ft    22 ft to infinity
>   3.5       34       17    to infinity
>   4         30       15    to infinity
>   5.6       22       11    to infinity
>   8         25       12.5  to infinity
>  11         11        5.5  to infinity
>  16          8        4    to infinity
>  22        5.5        2.8  to infinity
> 
Hi George,
Your post started me thinking and looking at two Realists I have
(one a 2.8 and the other a 3.5 with DEP and DOF scale). I was
trying to find a way to use Hyper focal without memorizing or
taking one more sheet with me. It is interesting in that if you
simply set the focus to infinity for the selected aperture, the
focus distance reads fairly close but not exactly as what you
posted. Even more interesting is that the two cameras do NOT
agree. Are there some differences in DOF scales or is it because
of the differences in the 2.8 and 3.5 lenses? See the table below
that I modified.

Aperture  Focus at  Infinity point set  Infinity point set
                    to aperture (2.8)   to aperture (3.5)
--------  --------  ------------------  ------------------
  2.8       44 ft       35                      n/a
  3.5       34          n/a                     35
  4         30          25                      n/a
  5.6       22          22                      25
  8         25          14                      19
 11         11          12                      14
 16          8          9                       10
 22        5.5        DOF scales do not go past f16

Please note that the 2.8 does not have a f3.5 marking on the DOF
scale as well as the 3.5 does not have the (obviously f2.8) or
the f4 markings on the DOF scale

Bill Stickley

P.S.
On your original table it appears that your "Focus at" figures
for f5.6 and f8 are transposed?


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End of PHOTO-3D Digest 2954
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