On 2020-10-17 9:20 PM (-4), Kenneth wrote:
> 
> My understanding is that 6500K is the 'standard' color temperature for a
> monitor; take a look here...

My monitor is set to sRGB with a white point of D65 (6504 K), but I also 
have an app that lowers the color temperature to 3500 K at night.  Aside 
from the greens appearing more vivid and green shades less easy to tell 
apart, I barely notice the change; my eyes adjust, and my sleep is 
probably better for it.  Of course, if the app abruptly quits (like when 
I accidentally shut it off just now while checking the settings), the 
difference is shockingly.  It's like the whole computer turns bright blue!

Prior to my current computer, which has a backlit LCD with an sRGB 
preset, I had manually set the gamma curves using clipka's gamma 
checking scene and a few test patterns of my own as benchmarks.

> In POV-ray, I presently use assumed_gamma 1.0, the long-recommended value (along
> with srgb colors rather than linear rgb.) But one of the new nagging questions
> that I currently have is about the use of the newer assumed_gamma srgb, and what
> effect *it* may have on a rendered scene. The documentation isn't clear as to
> why it's an alternative. Since it is nearly a 2.2 gamma, it is bound to have a
> rather profound effect, at least in the render preview. I've never used it
> before, but I plan to run some tests.

As I see it, assumed_gamma srgb is useful for updating legacy scenes 
that did not have an assumed_gamma, so they would run without warnings 
in POV-Ray 3.7, or at least render predictably in any POV-Ray version. 
(assumed_gamma has been available since 3.0, if not earlier, but 3.7 was 
the first version to fuss about it.)  With all the tweaks necessary to 
get the lighting right in the original scene, inserting assumed_gamma 1 
into a legacy scene and slapping srgb on all of the pigments is unlikely 
to end well.  Short of a rewrite of the entire scene (which some POVers 
have done), it's best to just make explicit in the code the sort of 
monitor it was developed under.

At least that's my take as someone who has used assumed_gamma 1 from the 
beginning.  Some POVers (I can name a couple) prefer an unrealistic 
gamma for artistic reasons.

But assumed_gamma 2.2 (or 1.8 or whatever) would be used for the same 
reasons.  I guess assumed_gamma srgb was added for the sake of ungamma'd 
scenes that were developed with an sRGB monitor.  Or maybe it's just for 
completeness.  I don't know.  Maybe Chris Cason knows?

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