P3D Re: realist vs revere DOF

[Eric Goldstein <egoldste@xxxxxx>]

Dick Twichell asks:

> Also - I
> believe that not all Realist lenses are 35mm FL.  If I recall correctly
> a conversation with Charles Piper a few years ago, some of the Eastman
> lenses had a slightly longer FL.  Can anyone confirm this?


Ektars are marked as 36mm!

BTW, I think the answer to all the questions regarding descripencies in
DOF scale markings have nothing to do with the esoteric but the
ordinary. DOF and the transition from sharp to blurry is not discrete
and the parameters for judging what's sharp or not have to do with
magnification and viewing conditions, which vary! It is interesting that
Revere and Kodak DOF scales are 2 stops more generous than the Realists;
Wirgin and Belplasca scales are one stop for generous. One finds this
sort of variation on countless cameras and lenses. To my eyes the
Realist markings are more real world for our viewers; it ises f/1000 as
the COC I think, which is a common standard for 35 mm...

Those interested in learning more can check out the on-line DOF
calculator...

http://www.par.univie.ac.at/~bob/photo/DOF.html

This uses f/1720 as the acceptable COC limit, and so stated DOF is
reduced even from the Realist scale.

My old time Rollei IBs state their tables were based on f/1400 for 6 x 6
and f/2000 for rolleikin (35 mm)!!


Eric G.


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