But just as an example. The other day I visited the Huntington with my dear friend Molly Lipsher. While we were there, a painting caught my attention. I am not particularly fond of it, it's very nice and all but what attracted me to it was the subordination of the whole painting to one note of very saturated color. This is exactly the kind of thing a "garyscale map" in Photoshop might not resolve if taken from a photograph.
Here is the original "The Last Gleanings" by Jules Andre Breton.
And here is the Photoshop treatment of the painting as I explained in my posting before. In the grayscale version you would never guess the prominence the red sun in the real painting. The chromatic saturation stands out more than the tonal value so while the whole painting hangs on that touch of red ,tonally speaking, it's not even an accent.
Ah, but that's not all there is. In the image bellow I used the "levels" adjustment in Photoshop to eliminate all the middle and low reds, basically leaving only the top saturated reds. Not surprisingly, the sun glows now like a traffic light. Sold!