Saturation vs Channel Mixer

[Nicolas Hanson]

What is the difference between raising the saturation and going to the channel mixer and raising the red only in the reds, raising the green only in the greens and blu in the blues?

[Dylan R. Hopkin]

Others have stated that increasing the values for each channel in the RGBmixer gives “cleaner” results than just increasing saturation. I haven’t compared the differences myself.

But increasing saturation using the A and B-channels in a LAB-node does give slightly more separation between neighboring hues. I used it on a pizza-commercial once, there the client had graded the commercial at a different facility first and wasn’t happy if the separation. They did a new grade at our facility. Since I had read about using LAB both at mixinglight and several photoshop-tutorials I thought, what the hell, it was worth a try. It looked slightly better, although we are talking small differences. (Meatballs and dark-cheese).

The client was happy with the regrade, that’s what matters B.)

Try LAB and see if it gets you a “better” result.

 

cheers

Dylan

[Cary Knoop]

Saturation in RGB solely depends on the largest and smallest channel value so it really does not matter what controls you use.  Obviously the channel mixer has more flexibility but if you are going for saturation without changing the luminance or hue it should give the same results.

I would be careful with L*a*b.  While this colors pace is unquestionably superior in modeling the perceived distance between two colors scaling *a and *b can cause hue changes, notably blue becoming purple.

At the end it all boils down to creative intent but it is important to be aware of potential gotchas with L*a*b.

A simple trick to compare the different methods is to create a layer node use a method for each node and use a Difference Composite Mode in the Layer Mixer to observe the differences.

 

Edited February 5, 2018 by Cary Knoop