11-26-2019, 10:21 PM
(11-23-2019, 01:14 AM)marco-gimp Wrote: Thanks Ofnuts; I'm now investigating this tool.
Okay ... I think that I have understood it.
The scale is 256.
Therefore a fully black image would have a value of 0
A slightly less black image might have a value of 2.56
This would indicate that the slightly less black image was emitting 1% of light
... and absorbing 99% of light.
This is the required tool.
Thanks again Ofnut
No...You can tell that there is a difference, and increasing values mean increasing difference but it's likely not linear by default. The 0..255 scale is "gamma-corrected" so the true value (in a 0.00-1.00 scale) is more or less pow(x/255,2.2) (or is it pow(x/255,1/2.2)?). In Gimp 2.10 you can work in "Linear light" but even then the values are whatever is needed to make the image look right, and not an accurate measurement of incident light.