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In article <3909A3B3.BF05149C@inapg.inra.fr>, Gilles Tran
<tra### [at] inapg inra fr> wrote:
> For what I read here,
> http://www.geocities.com/SiliconValley/Haven/5179/
> it's equivalent to PSP and Picture Publisher H/M/S modification,
> including the color balancing alteration. So we're basically talking
> about the same thing.
> The really nice thing about H/M/S balancing, for a non specialist of
> photo touch-up, is that it is very simple to use (unlike color
> balancing or even color saturation) and, usually, a subtle extension
> of the shadow range is quite enough to enhance nicely a picture. So
> if something of that sort could be implemented in pov, it would be
> nice to have it done along the same lines, or, if this can be done
> with a generic model, to ensure that this model can be used in a
> macro that does it with the H/M/S logic. Obviously, such a generic
> model could be extremely powerful and improve many pov renders in a
> dramatic way.
A dynamic_range filter, which would take two values and scale the input
so that the min value is at 0 and the max at 1? I think it could
probably be done easily with the add and multiply filters, though. Maybe
package it in a macro, this seems to work right:
#macro DynamicRange(Min, Max)
clip_colors {Min, Max}
add {rgb -Min}
multiply {rgb 1/(Max-Min)}
#end
Another filter that might be useful would be a "curves" filter, that
takes a spline(or a color_map?) and adjusts the image according to it.
> In fact, I wonder why most pov pictures use such a narrow range. I
> have always noticed that pics from other renderers tend to be
> crispier : is it possible that these renderers include some
> self-correcting algorithm that would stretch the range whenever it's
> needed ? Note that this is a general statement : HE Day pics, for
> instance, always seem quite contrasted already.
I think that is mostly because HE Day is better at lighting than most
people. I tend to use ambient 0 when possible, and rely on multiple
lights and radiosity(thanks to Nathan Kopp!) to get good lighting. I
find it greatly improves shading and shadows.
--
Christopher James Huff - Personal e-mail: chr### [at] yahoo com
TAG(Technical Assistance Group) e-mail: chr### [at] tag povray org
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/
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