WobertC • Adobe Community Professional, Oct 03, 2020
The 'Color' Range mask does what you ask.
By placing a 'pin' on light tones of a color with the dropper tool- you select only those luminance tones.
My example in screen-clips:
1) The original image
2) A Gradient applied over the whole image, with the overlay showing as 'Red'.
The first dropper pin is on the lightest tones of 'Blue':
3) A second dropper pin is applied to the darkest blues at the top of the image. Note the Mid-tone blues are not fully masked!
4) A third dropper pin is ap...