"David Littlewood" <david@nospam.demon.co.uk>

wrote in message news:Czj2kuB4hPu$Ewm3@dlittlewood.demon.co.uk...

> In article <10c1a061.0311170606.1fa25f65@posting.google.com>, Collin

> Brendemuehl <dpcwilbur@excite.com> writes

> >DOF is controlled primarily by 2 things --

> >focal length and aperture opening size --

> >and secondarily, less significantly by

> >optical design.

> It depends on focal length, aperture and object distance (plus, if you

> are going to be picky, final image size).

>

> How do you believe the "optical design" affects DOF? Presumably you mean

> the arrangement of lenses chosen as the basis for the computation

> (Tessar, Planar, Gauss etc.). I have never seen any suggestion that it

> does depend on this (and don't see how it could) but if you know

> something to prove it does, this would be interesting.

> --

> David Littlewood

I think the poster didn't mean it this way, but DOF can be affected

by lens resolution, with the sharper lens having slightly less DOF,

everything else being equal (though the resolution difference would

need to be very considerable). BTW, I did not see in the thread

above any mention of the ability of most 4x5 cameras to have the

plane of focus shifted away from being parallel with the film - and

this can appear to increase DOF for a given aperture in some

situations...

--

David Ruether

d_ruether@hotmail.com

http://www.David-Ruether-Photography.com