In article <=qAEOc9gmlpxWf8+V87kmu2mtM4W@4ax.com>, Glen Berry 
<7no### [at] ezwvcom> wrote:

> I think there was another reason for blurring the negative, in
> addition to worries about film alignment or grain. I think it had to
> do with preserving the high frequency content and "local contrast" of
> the image.

Ah, I see. That way, the smaller features would not be "corrected" out 
of the image, but the larger areas would still be affected.


> I'm trying to find some technical reference material on the subject,
> but haven't yet. I've had to work strictly from my personal memory so
> far, but I'd like to find some technical documentation on this
> subject. The internet turns out to be a very poor place to search for
> this information, because practically all the search engine hits refer
> to the Photoshop unsharp mask effect.

I did a search with Sherlock, and found this page:
http://www.ittc.ukans.edu/~jgauch/kuim/contrast/unsharp.html
This might also be relevant:
http://www.computer.org/proceedings/icip97/8183-439.htm

Some other interesting stuff:
http://www.ph.tn.tudelft.nl/Courses/FIP/noframes/fip-Basic.html
http://perso.club-internet.fr/legault/ip.html


> Also, there *are* things in POV-Ray image that could react to this
> process in a way similar to film grain. High frequency content such as
> crand, fine textures, very small objects, and media "graininess" come
> to mind. Without blurring, I think we would be removing, minimalizing,
> or distorting much of the high frequency content in the image. This
> isn't usually a wanted by-product.

Yes, I understand the technique a bit more now.

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/

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