Must the Channel Mixer always total 100% ?

[Rich54]

I’ve been studying a lot of tutorials (Lee Varis; PHLearn) about skin retouching and practicing my skills on downloaded images of people with bad skin and acne. I’m trying to achieve a natural look, not the highly-polished fashion magazine look, and I discovered that you can achieve a decent degree of skin smoothing—before any blurring, clone-stamping or spot-healing—by using a Channel Mixer adjustment layer. Here are the steps I took:

1. In the original image, the Blue channel contains the highest contrast and the worst of the mottled, blemished skin. The Red channel shows almost no bad texture but is very washed-out. The Green channel is somewhere in between.
2. I added a Channel Mixer adjustment layer above my image and set it to Monochrome. I adjusted the Blue channel (with the worst skin texture) to zero and experimented with the remaining channels, finally landing on Red=66%, Green=18%, Blue=0%.
3. The Channel Mixer is now a B&W image, but setting the blend mode to Luminosity brings back all the original color, re-mapped to the new tones and new contrast. It achieves natural-looking smoothing without overtly altering the image by blurring, etc.

My question is this: Inadvertently, the channel mixer settings shown above total only 84%. Did I do anything wrong there or somehow discard some of the image information? Is the channel mixer always supposed to total 100% across the 3 channels?

 

[Tom Mann]

For even finer control, use a black and white adjustment layer (also set to luminosity blend mode) instead of a channel mixer layer.

And, to answer your question, if the sum is not hundred percent, all that will happen is the average brightness will be different from what you started with.

T (presently in sunny New Mexico! )

 

[Rich54]

Thanks. I'll try the B&W adjustment layer and see how that goes.