Layer Mode - Hard Light *AND* Desaturated?

Thank you Mylenium. I do appreciate the help. This is a little complicated so bare with me. This might be painful lol:

Your suggestion to use a hue/value adjustment layer on top works! It's perfect. But there's one last hurdle.

Let me try to explain this:

On the bottom layer I have painted a solid circle with a hard brush, using a yellow color.

The layer above is set to Hard Light. Now when I paint on this layer, it adds highlights or shadows to the yellow circle beneath, and the intensity of those shadows/highlights depends on the value of the color I am using. Using grayscale colors(shades) work perfect for this. But if I use anything other than grayscale colors (i.e. any other color), then the shadows/highlights that I am painting become saturated with color - not what I want. So, I want to restrict this hard Light layer to grayscale only when painting on it, so that even if I paint with colors on it, it forces those colors to completely desaturate and become grayscale only. 

So, your trick worked - above the Hard Light layer, I added a Hue/Sat adjustment layer, and pulled the saturation slider all the way to the left - and it works. So I now have 3 layers in total. The bottom is the solid color, the middle is the Hard Light layer for painting highlights/shadows, and then the top layer which is the adjustment layer which forces the Hard Light layer to be desaturated. Perfect.

Here's the problem:

I need the the shadows/highlights to be clipped to the bottom layer (yellow circle). So, I added a clip to the two top layers and the clipping works, but the yellow circle on the bottom is now desaturated - no color shows through.  The problem here is within the clipping masks, but I don't know how to solve this.

I know there are other ways to do this very easily, but for the time being I need to go this route (I'll explain later).

Still with me? Thanks! Is there a way to do this?

You cannot reverse the internal logic of how image masks work. You'd be putting in question 50 years of computer graphics or going back even further 100 years of photography/ making movies. Opaque areas are always white since this is derived from "blocking" light on exposed film with cardboard whereas unblocked areas would be fully exposed and turn black. That's how it came about. Otherwise I woulkd advise against making things too complicated and unpredictable. You will have much better luck controlling this if you simply duplicate the actual layer with teh blending mode and adjustment layer on top, and mask outh both by applying a group mask, putting them inside a smart object or whatever works best for you and then "brush it on" as needed by ways of manipulating the mask.

Mylenium

Hi

https://forums.adobe.com/people/boo+radley+2013  wrote Question 1: If I switch a layer's blend mode to Hard Light, is there a way to make it so that the layer is also desaturated at all times? So that if I paint on the layer with a saturated color (green for example), that it will only paint the *value* of that green?

I don't understand what you mean by the "value of green" - the Lightness value , the Hue …..? You could combine an adjustment layer e.g. Hue and Sat ,clipped to the pixel layer (Alt-Click on the border between the two in the layers panel) , then set the blending mode of the pixel layer to Hard Light

Question 2: If I use an adjustment layer, then painting on it using a black color will *show* the adjustment, and white will *hide* it. Can I reverse this somehow, so that white will hide it and black will show it?

Any layer mask - shows the layer (or adjustment ) where white and hides the layer (or adjustment) where black. You can't change that - although you can of course use Ctrl+I to invert the layer mask

It is not clear what you trying to achieve with this. Can you post a description with images that show what you are trying to achieve - that way we may be able to suggest the best way

Dave