Because displacement maps alter the geometry of the surface, the textures you use as the map should not contain jagged edges (aliasing) or noise.
To filter out aliasing and noise before you displacement map a surface, see Texture filtering.
If you must use a texture with a small amount of noise for displacement mapping, use Feature-based Displacement mapping, and adjust the Texture Threshold attribute.
Occasionally when you map a texture with distinct features to an object, the volume, or size, of the object could change.
To adjust this problem and preserve the object’s volume (size), use a negative Alpha Offset value for the texture to bring the size of the geometry back down (such as -2). You may also have to adjust the file texture to get the desired result.