Chris Peterson wrote: ↑Sun Aug 06, 2023 5:34 am
VictorBorun wrote: ↑Sat Aug 05, 2023 10:11 pm
Chris Peterson wrote: ↑Sat Aug 05, 2023 9:31 pm
The egg shell has a pretty uniform hue. The
image of the egg does not because of the intensity variations. Even with a hue created by a very narrow wavelength, there is no single color (or meaningful RGB representation) because the actual color is defined by intensity as well as hue.
here's a fragment of the pic of a robin's egg
Robin's Egg-.jpg
You can see that a point of the sun's reflection is white; here the random movement of a photon scattered by CaCO₂ crystallites is minimal and chances for an ink molecule to absorb that photon is minimal.
The wider the angle from the sun's reflection the greater is the distance a typical photon travels through the egg's shell material before coming out along your line of sight. That is exactly what thickening a dye means.
There's a limit to that thickening here: a robin's egg has a thin shell with a budget quantity of ink and just white matter beneath.
So the longest travellers among photons get to pass through the shell and scatter from the white.
You can see just white to pale cyan to cyan-blue, no blue to dark violet to black
The hue is uniform. You're referring to a geometric effect.
You are right and I was partly wrong.
Here I try to compare two ways to make the picture fragment of the robin's egg more uniform:
1) to adjust the input range of RGB; that's a transformation that keeps the hue
2) to adjust gamma; that's a transformation that keeps the sort of the dye and just makes it thinner or thicker
![hue or dye 0.jpg](./download/file.php?id=48050&sid=513d47ef48f62e6a1ed175542ded498a)
- hue or dye 0.jpg (7.24 KiB) Viewed 2924 times
![hue or dye - input range.jpg](./download/file.php?id=48049&sid=513d47ef48f62e6a1ed175542ded498a)
- hue or dye - input range.jpg (8.76 KiB) Viewed 2924 times
![hue or dye - gamma.jpg](./download/file.php?id=48048&sid=513d47ef48f62e6a1ed175542ded498a)
- hue or dye - gamma.jpg (8.43 KiB) Viewed 2924 times
You can see that both ways are successful and that the hue-preserving one is doing even better, discarding my claim that there is no hue.
There is a hue, and it is cyan, and it is primary.
There are 6 primary hues: red, yellow, green, cyan, violet, pink.
A dye of a primary hue can be thinned or thickened without changing its hue.
I still claim that there is no hue to this APOD cyan nebula: it is a blue (a.k.a. an indigo), not a primary stuff, showing the range of hues cyan to violet.