Time for another tutorial. I've been meaning to write up this one for a while now and was prompted to finally do it when I used this technique on the photo above.
Grisaille (pronounced griz-eye) is a painting technique that means to paint in B&W in order to establish the form of a subject. Hue (what most people refer to as color) can confuse the eye in terms of tone (dark & light) because intense warm hues can perceived as being lighter than they are and cooler hues tend to recede, appearing darker than they are. By painting with only tone the artist can define the form of a subject without reference to "color" and gain a better understanding of the form.
Often this is done only in "studies", references for later paintings that are in color (a combination of tone and hue) but some artists have used the grisaille as a tonal base for overpainting with translucent hues. The grisaille establishes the tone and is seen through the translucent glaze of hue resulting in the color.
I wondered whether something similar could be done in Photoshop and found a technique that I call "Reverse grisaille". It is reverse grisaille because although I could not find an effective way to have a B&W layer show through a color layer, it is quite easy and effective to do the opposite.
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