Dual Hue/Sat Ad-Layers
- H/S* using Sat=0% (-100) to get greyscale
- H/S* set to Colour and uses H/S sliders to tweak
- Orignal photo
*Commonly called HSB. This is a misnomer and I am extremely guilty of it.
In the top H/S, Sat=0% (-100) to get grey. Photoshop uses Lightness, and Lightness = (MaxRGB - MinRGB) / 2.
R=127
G=190
G=255
Will give Lightness=75%.
In the bottom H/S, Photoshop will use 30%/59%/11% to get Luminosity.
You are using something like this:
hue2grey.jpg
Luminosity first, then H/S. Same for Lightness and Brightness. In Colour mode, it's 30/59/11. This is why I always put Lum on top in the Layers palette.
When you manipulate the H/S in the bottom H/S Ad-Layer, you are manipulating MinRGB and MaxRGB. This will then be 'pumped through' (MaxRGB-MinRGB)/2 for a final greyscale value.
I say leave the bottom H/S Ad-Layer in Normal mode.
Use the drop-down to select a Hue range.
Then use the Lightness slider to tweak to final greyscale value.
Want reds to be darker?
Then make reds darker with Lightness as oppossed to using H/S.
Simple and direct.
Also, never forget that Adjustment Layers can be masked.