Request for RGBY tone curves


This kind of curves look overall like the standard rgb curves but they could help with very saturated colors or with strong primaries.
They work in a similar way of the rawtherapee’s luminance curves, the difference is that we process the rgb input too with curves , find the (rgb+curves) luminance and “merge” with the (input luminance + curve)

Example from a Playraw, look at the car’s rear lights


rgb curves

rgby curves



Y_input = R * 0.2126729 + G * 0.7151521 + B * 0.0721750

Y_output=Y_input + curve

RGB2=RGB + curve    

Y2=R2 * 0.2126729 + G2 * 0.7151521 + B2 * 0.0721750 (luminance of RGB2)

RGB_output= (RGB2  /  Y2) * Y_output

It could be possible to test these curves in rawtherapee ? :slight_smile: