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Re: Photo Image out of focus

At 09:42 6/24/01 -0400, Ludwik wrote:

I can think of some helpful conditions - an emulsion latitude
capable of capturing the intensity contributions of several
source contributions - I seem to recall the appropriate measure
of this property is the Hurter-Driffield curve. The fact that
it *is* a curve is unhelpful.

1) What is the Hurter-Driffield curve?
2) The first sentence would be more clear to me if the word
"capturing" were replaced by "distinguishing". Is it not true
that a camera film always captures contributions from several
sources? I must be missing something important; what is it?
Ludwik Kowalski

Here are some Google hits on Hurter-Driffield, to give a feel for the
contexts in which the H-D curve is mentioned. The third URL is
a product description written from a workmanlike physics viewpoint,
and includes a reference to Hurter-Driffield's original paper.

Remote Sensing Tutorial Page 10-2

CS563: Recovering High Dynamic Range Radiance Maps From Photographs

photolithography paper in SPIE

To answer Ludwik's second point - the emulsion misses intensity
contributions if they are overlapped too numerously to place the
resulting emulsion density (or other detector response) in the
linear part of the H-D curve.

brian whatcott <> Altus OK