Archived posting to the Leica Users Group, 1999/09/11
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On Sat, 11 Sep 1999, Ted Grant wrote:
>
> What think you folks? The student is waiting, because I told him I'd
> present his question to the worlds "great photo minds for an answer!" :)
>
Not that I fall within that category, but that has never stopped me from
proffering an answer ;)
As I understand it, `focus' has to do with the film plane. When we talk
about focussing on a subject, it is not the fact that the lens is set to a
particular distance that is meant, but that the light rays from certain
plane infront of the lens converge at the plane of the film.
Consequently, `depth of focus' should refer to the film plane, not the
object space, or else we would be mixing two different definitions of
`focus', one to do with the film plane, one to do with the object space.
`Depth of field' is used to refer to the object space, to avoid this
confusion of the term `focus'.
OK, not the most technically clear presentation, but isn't that the
fundamental distinction? Focus has to do with the film plane?
M.
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Martin Howard (__) (__)
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