2 - 255 Reduces the number of possible intensities in an image: it rounds the color values. The effect is mostly apparent with a low number of levels. posterised image example: simulate the 216-color "web" palette using 6 levels. simulate a 15-bit display using 32 levels . Number of possible levels per channel. The levels are equally spaced, with the lowest at 0 and the highest at 255 the minimum number of levels is 2 and the default value is also 2 original image