Will W wrote:
> "Edward Coffey" <eco### [at] alphalinkcomau> wrote in message
> news:3E9### [at] alphalinkcomau...
> 
>>Will W wrote:
>>
>>
>>>That sounds like an alternate approach that could work. However it isn't
>>
> the
> 
>>> one that's implemented in POV-Ray.
>>
>>I maintain that it is.
>>
> 
> <snip good example>
> 
> Yes, you can force POV to do it this way. But it is not the way the gamma
> tools were desigend to work.
> 
> Here's a counter example: Roll the clock forward about two years. In 2005
> you do up some wallpaper on your trusty old Mac with its gamma of 1.8 and
> send it tou your friend who is still using her trusty old PC with its gamma
> of 2.2. She emails you an immediate response saying that she's delighted,
> the colors are so vibrant! Neither of you think about gamma.
> 
> Why is this? Where has the gamma problem gone to?
> 
> It went into history. Although neither you nor your friend have updated your
> hardware in quite a while, you are both staying current with software and
> recent trends. So naturally you sent her the image in a lossless compression
> ..png file, which is so much better than the lossy old jpg files everybody
> used to use. The png file also carries the gamma information so it can tell
> whatever machine it ends up on how to best display itself. No problems.
> 
> *That* is what POV's gamma system is designed for. Eternal universality--
> what a concept.

You are quite correct that with file fomats that record the gamma of the 
stored image this problem disappears altogether, you can render at a 
gamma of 1.8, your friend's software sees that the image has a recorded 
gamma of 1.8 and does the necessary conversions to display it properly 
on their gamma 2.2 system. Of course, using such gamma aware software 
will result in correct display of all the PNG images I make using the 
procedures I have described here. These procedures are not 'forcing' POV 
to work in any weird and unnatural way, they are simply using the 
features to do the job they were designed for - to get around the 
limitations of non gamma-aware formats while not causing any detriment 
when using gamma-aware formats. I am curious to see a concrete example 
of how you believe the gamma controls should be used *today*, since the 
only suggestion I've seen is changing assumed_gamma from 1 to 2.2 when 
changing the target from a gamma 1.8 system to a gamma 2.2 system, which 
results in effects opposite to those which are desired.

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