So I have generated this simple height map to test my add on:
That's the node setup and the result that I am having in Blender:
What is happening here (basically, that's a theory, I did not analyze the actual pixel values programmatically): Blender Bump node is interpreting each slightest variation in the pixel value (say, 0.985 white and 0.99 white) as variation in height. What you have as a result are the ugly cutoffs. By the way, a similar question with the same problem, unsolved: height map brings weird result
Now, if I do converting in CrazyBump, I have the opportunity to ignore small details, and, if I convert with CrazyBump, the map is displayed correctly in blender. By their nature, any height map, even 16K will not be absolutely smooth because the set of possible heights is a set of discrete values, it will never be smooth. The task of an algo would be to produce smooth normals from this. And this is what Bump node obviously does not do. Any suggestions? (using other software does not work, I want to achieve it specifically in the node editor of Blender, for any BW map)
and just to prove the point: if I twick the small details all the way up in CrazyBump, I will get essentially what the BumpNode in Blender is doing: overexaggerating non-significant value variations: