# How bump node reads images in Cycles

When I plug an image to the "bump node" ( or "Displacement" ) Does it consider the black value as 0.0 height or the gray ones (0.5,0.5,0.5)

It doesn't matter at all.

The only thing that matter is the difference between the values. The two sets of pixels in the image above will give identical results, because the difference between black (0.0) and grey (0.5) is 0.5, and the difference between grey and white (1.0) is also 0.5.