In article <3faf4d7a$1@news.povray.org>,
 "Marc Jacquier" <jac### [at] wanadoofr> wrote:

> Your monitor
> > can only display colors with a limitedd range of brightness and most
> > file formats only store percentages of maximum brightness rather than
> > absolute brightness, so the colors are clipped at output.
> But pixels colors are computed from light color>fade due to distance>object
> pigment/diffuse properties... so not inevitably clipped.

Distance fading is off by default and scenes usually have at least some 
pigment/diffuse properties that come close to white.


> If you want maximum dynamic range in your image (i.e white highlights and
> black most dark shadows) you can multiply your light color.

By what?
Yes, you can pack more information into the output image by making sure 
the lighting is dark enough that clipping is minimized, and then 
post-processing the scene to get the normally lit portions (which are 
now very dark because of the light scaling) to show up right. However, 
this has bad precision effects...a 24-bit image has 8 bits per color 
component. That's 256 levels from black to 100% intensity. If you use 
100% to mean 2x max viewable intensity, you've just limited the normal 
[0, 1] range of lighting to 128 levels of intensity. If 100% means 10x 
max viewable intensity, you limit it to 25 levels.

You could render multiple images at different color scales and combine 
their data, but your best bet is to just use a patch that adds a high 
dynamic range output format.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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