I want to do some shading exercises and I have a 5 values scale from white to black with 3 shades of gray.
How can I convert a picture to have only 5 colors in photoshop?
I know how to convert it to gray scale but I don’t know how to take it further to only 5 colors.
There are many methods including using Image > Adjustments > Posterize, or alternatively Filters > Artistic > Cutout – then you could tweak it with a levels or curves adjustment layer to make the lightest colour white, and the darkest black.
Another method in which you can control all the colours exactly is to convert a greyscale image to Indexed color mode. Then simply create a custom colour table.
Another possibility is to create a gradient, and apply it as a gradient map adjustment layer.