Re: Photo Image out of focus

[brian whatcott <inet@INTELLISYS.NET>]

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
<http://www.sbg.ac.at/geo/idrisi/remote_sensing_tutorial/rst.gsfc.nasa.gov/s
ect10/sect10_2.html>

CS563: Recovering High Dynamic Range Radiance Maps From Photographs
<http://davis.wpi.edu/~matt/courses/radiance/>

photolithography paper in SPIE
<http://www.finle.com/product_information/publications/3677-46.pdf>

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 <inet@intellisys.net>  Altus OK
                Eureka!