Author Topic: Colour Adjust Sliders  (Read 257 times)

Offline ajcgi

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Colour Adjust Sliders
« on: February 21, 2018, 01:21:41 PM »
The colour adjust shader has 2 pairs of sliders. When Black is black and white is white, both pairs mimic each other, but if a colour is set, they no longer do. This make us wonder... why? What does the bottom number here represent, numerically?


Offline luvsmuzik

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Re: Colour Adjust Sliders
« Reply #1 on: February 21, 2018, 03:45:16 PM »
For a beginner like me, it means when you put close to the full value of a color in either position, it changes the effect of what is being done. At full value black and white the effect is 1. Changing either color to clamp to changes that. Red is pretty close on the color wheel to full value black so your effect seems to be decreased significantly. Pink has quite a bit less effect than red in the end result. Are you using color adjust to stabilize, mix or mask with?

Offline Matt

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Re: Colour Adjust Sliders
« Reply #2 on: March 03, 2018, 04:52:53 AM »
In this shader, the lower scalar value is the median of the RGB components. So if the RGB values are RGB(0, 0.1, 0.5)  the scalar value will be 0.1. This applies to white point, black point and gamma.

It's been about 16 years since I wrote this shader (can you believe it?!) but I think the reason it works this way is to allow you to shift the colours up or down without changing the spacing of the RGB values within the colour, and that can be helpful when dealing with negative black points. So let's take the example I gave earlier where the colour is RGB(0.0, 0.1, 0.5) and the median is 0.1. If you change the median to -0.4 all the values will be shifted by -0.5, so they become RGB(-0.5, -0.4, 0.0). This used to be a lot easier to see when the UI showed us all 3 RGB values (that changed before TG2 was released).

The number that's on the same line as the colour swatch works just like colours elsewhere in the program. It is the largest of the RGB components. But I wasn't satisfied with how that worked for black points.

Matt
« Last Edit: March 03, 2018, 04:58:43 AM by Matt »
Just because milk is white doesn't mean that clouds are made of milk.

Offline ajcgi

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Re: Colour Adjust Sliders
« Reply #3 on: March 05, 2018, 10:15:44 AM »
Interesting. I think I understand that now. Cheers both!