What properties of a colour image might make it suitable for desaturation?
I can see that some instructor is having their students memorize rules instead of teaching concepts which will work on any continent in the world and produce predictiable, marketable images every time the shutter release is pressed. The ONLY time I use desaturation is when I am processing an RGB file and making it a black and white one. Then ALL the colours get -100 saturation and the black threshold is adjusted, white threshold is adjusted as well and then I do a little thing with the mid-tone slider to make the image just right for my taste. Even when working with strong reds, greens or blues that may get clipped when printed, I am very careful when doing ANY colour adjustments, whether it is hue, saturation or contrast.
