I have just started using Blender a few weeks ago and I have been doing ok with it until recently when I changed some setting and now I can't get displacement to work on image textures.
Before I could use displacement images on bricks for example to get nice 3d textures with each brick raised out of the surface. But now when I add an image in the node editor with a displacement image and hook it up and add subdivision surface modifier and displacement modifier I can't get the nice 3d effect. Changing the strength or midlevel just seems to change the x and y displacement. Please help. I've attached an image of my workspace. Also I would like to know if it's possible to get displacement effects not just on each brick but also on the contours and ridges within an individual brick?
you have not connected the Texture Coordinate to the Displacement Texture, would guess that causes the problem. Also switching the Image Texture Node from "sRGB" to "non-color data" give more accurate results
You're displacing the mesh geometry, pre-render, with a Displacement modifier, and furthermore, displacing the render-evaluated geometry at render-time, with a Displacement shader (which only Cycles will implement). The combination is certainly not what you want, here, so, go one way or the other.
If you choose to use the modifier, you will probably need more subdivision to pick up a reasonable amount of the detail from the height map.
Maybe you have made your wall from a cube scaled in Object Mode? (While modelling, always scale in Edit Mode :) ) This will have scaled the wall's Object space (its axes, you can switch them on in Object Properties > Viewport Display to have a look), as well as its mesh. That scales the normals, as measured in Object space, too, and the effect of displacement. Try CtrlAApply > Scale to fix that.