in news:3B731A2A.4B783AE3@pp.htv.fi Kari Kivisalo wrote:

> Outputted from pov as 48 bit linear. Compressed in Photoshop
> using transfer curve (intensity only) based on a film response
> curve from Kodak site. It's a typical compression curve. Then
> gamma 2.2 corrected and converted to 24 bit.

 I'm wondering a bit about what you are doing, but that can be the 
result of me not knowing how povray works internaly.
 If I have a rgb 1 sphere and a rgb 2 lightsource in the camera 
position, there is a spot on the sphere with a brightness > 1. Is this 
spot immediatly clipped to 1, or does povray calculate with the higher 
found value. Example, the sphere is reflected in a mirror, will the 
mirrord spot have a brightness >1?
 How are the color values that go into the file determined? Is 
everything >1 just clipped to 1? Do I understand the 48 bit output 
right in that it just has more steps between 0 and !, but has no 
influence on the contrast range?
 If the above is not terebly wrong, it seems to me that what you are 
doing is adjusting the contrast range of the mid tones only, as there 
is no information about the higjlights in the file.
 In photography what we do, is adjust the complete contrast range of 
the scene so it fits in the range of the paper the image is printed on. 
In a studio situation this is simple, you contro; the range with the 
lighting, just as you do in POV-Ray. In outdoor scenes there are 
different tricks.
 Lets take a high contrast scene, a marrying couple. The dress is 
white, his suit is black. The contrast is too big for our film to 
catch. Now we over expose to make shure that we get all the details in 
the shadow. If we develop this film normaly, the resulting negative is 
not usable, it has a too high density and contrast to print. So we 
develop shorter. The detail in the shadows will be just there, the 
highlights will not be developped completly, so the density is good 
there too. The negative can now be printed to normal photo paper. In a 
low-contrast scene the opposite is done, under-expose, over-develop.
 If this is what you want to do with POV-Ray it has to output all data 
linear and unclipped. Such a file woul be a good base for all kind of 
manipulations, contrast compression to view on a monitor or print. For 
printing the data could be split in a high key and low key part for 
duo-tone printing per colour-channel etc.


Ingo

-- 
Photography: http://members.home.nl/ingoogni/
Pov-Ray    : http://members.home.nl/seed7/

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