Am 10/28/2020 um 2:03 schrieb Kenneth:
> 
> When using assumed_gamma 1.0, and in POV-ray's preview render:
> 

When using anything but assumed_gamma 1.0 it makes no sense to use the 
srgb keyword anyway.

> If I want to *multiply* an RGB color,  rgb 0.7*<.3,.5,.7> would be OK to do.
> 
Sure.

> But if I want to multiply an SRGB color,  srgb 0.7*<.3,.5,.7> would NOT be the
> correct way to do it, to get the 'expected' color result (if I understand some
> of Clipka's older remarks); I would instead need to use a somewhat different
> multiplication scheme. Is that what these 'multiplication functions' are for--
> the way to properly 'multiply' an SRGB color?
> 
> Or is   srgb 0.7*<.3,.5,.7>  perfectly OK by itself?
> 
No it isn't. When using the keyword "srgb" you just tell POV-Ray that 
the following color term is "sRGB gamma encoded".
Multiplying any non linear color value does not only change the 
brightness but also the hue - and is therefor plain wrong.

I haven't used POV-Ray in years and never used the srgb keyword in my 
whole live (I switched to Adobe RGB a long time ago) so I'm not sure if 
it will swallow this syntax but at least you should get the idea...

#declare C = (srgb <.3,.5,.7>) * 0.7;

> Or am I way off base as to what the functions themselves are meant for?
> 

Yes, I guess this is what BE meant it for even if he called it 
"tone-adjusting" while in fact it is a brightness or intensity adjusting.



...and BTW I just stumbeled over your bold statement

[quote]
simply to get the color I 'visually' expect as
opposed to 'linear' rgb colors that are intrinsically washed-out in an
assumed_gamma 1.0 environment.
[/quote]

I used from the very start (more then 2 decades ago, I guess 3.0 at the 
time) assumed_gamma 1.0 (I already had some experience in the field of 
image processing) and no image I ever created suffered from a washed-out 
look. Some early images of mine did look ugly because my own bad choice 
of colors or bad arrangement of objects but these are no gamma related 
problems ;)


BTW during the early phase of POV-Ray 3.7 alpha development I had this
on my webpage:

https://www.lilysoft.org/Stuff/gamma.html

thankfully Christoph did make all the described workarounds obsolete as 
he improved the image file handling and also implemented an image file 
related gamma keyword as I did suggest there, so after the 3.7 release I 
removed any direct link from my side.

And BTW-2 your cityscape looks phantastic and things like this are still 
the strength of POV-Ray even when it has sadly fallen far behind as a 
render engine.


-Ive

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