Re: [Leica] DOF?

[Mikiro Mori <arbos@silva.net>]

Thanks, Richard and Mark for the responses.

At 9:12 am +0200 9/7/99, R. Saylor wrote:
>Any distance other than the plane of focus is going to be out of
>focus. The near and far ranges of the DOF are supposed to be the
>minimum and maximum distances for which objects will not be so out
>of focus that it will be obvious on a 8 x 10 print viewed at a certain
>distance (I forget how far that's supposed to be). The DOF formulas
>depend on the size of the circle of confusion, which is a measure of
>how out of focus something is. It is purely optical theory and doesn't
>take into account lens characteristics.
>snip

At 9:11 am +0200 9/7/99, Mark Rabiner wrote:
>This just got be thinking there was an article a few years back in a
>better photomag about how a dozen of photography's basic adages were
>said to be counterfactual.
>The First one I thought of here was the one third rule on depth of
>field. When shooting fast you go one third back from the front plane of
>focus with the idea being there would be 2 thirds after that point
>you've focused on behind it that would be in focus. A basic rule that
>most of us know and use and don't question but this guu took a handful
>of lenses from different formats and tested them and some were not even
>close and applying that rule to those lenses would not be smart.
>If that were the case how could a depth of field chart working on
>mathematical principles be really accurate?
>snip



I am beginning to understand better....@@;
So, DOF is calculated on the assumption that the lens has no abberations.
That's why we sometimes feel that lenses with the same focal length and f
stop (but with different abberations) give apparently different DOFs.

Mikiro