Screen Tone change without blending [+/-]

[Stray]

If the screen tone is changed ingame by the "Change Screen Tone"-Command, the screen has an 'add' or 'subtract' effect (I'm not sure). It's this blending effect which makes the contrast of the screen higher.
But I think it looks very odd in this way.

Example: ShowHide

Left: Normal pic without any changes.
Middle: RMXP - Making everything darker + keeping the colours.
Right: How I think it looks normal + everything gets darker. RPG Maker 2k(3) works this way.

I don't find good words for it. The rmxp-version looks so... 'rusty'.

[Blizzard]

The RMXP version decreases the intensity of the color channels, it does not reduce the saturation of the colors. If you want to reduce the saturation, you also have the "Tone" color component for that. Keep in mind that saturation/tone works on all 3 colors channels together, not just a single one. It's actually a somewhat weird cross-implementation for the HSL color model mixed with classic additive RGB. I'm too lazy to explain the details.

[Stray]

Spoiler: ShowHide

Isn't there a way to get rid of this effect?
The screen toning in RMXP darkens everything much earlier.
I know the trick with laying a black picture over the screen, but that isn't very helpful everytime.
Sometimes I need a tone with more different colours. Then it would be quite difficult to find the right picture tone.

[Blizzard]

Nope, it can't be done, it's how it's done internally. And frankly RMXP is actually the one that does it correctly. You can try experimenting with (-64, -64, -64, 128) or values like that. There should be a way to get a similar result. If you overlay a black picture, it uses simply alpha blending. But if you use the screen toning, it uses color multiplication which is done in a different way.

RGB = RGB_d * RGB_s

RGB = RGB_d * (1 - A_s) + RGB_s * A_s

s = source
d = destination, the color of the underlying pixel
RGB = red, green, blue components of the color
A = alpha component of the color

As you can see, it's not really the same formula. Sure, you can get similar results, but overall it's not really possible the reproduce the same color.

EDIT: If you want, you can try to cross-reference both formulas to get the closest possible result. (I am substituting the 1 - A_s for RGB_s here.)

RGB = RGB_d * RGB_s + RGB_s * (1 - RGB_s)

RGB = (RGB_d - RGB_s) * RGB_s

RGB = RGB_d * RGB_s - RGB_s²

RGB = RGB_d - RGB_d * RGB_s + RGB_s²

So using a black overlay picture is what you should actually use.

[Stray]

So i'll still have to do my fades with a black picture.
For toning with various colours I'll try it with your recommendation.

Thanks for your advice.