Displace modifier on specified region of hollowed cylinder Noobie here 
I have a hollowed cylinder (ie hole cut through top/bottom) and want to displace a small outer region of the cylinder with an image. The displace modifier tries to displace all verts of the entire object. 

How does one displace specific verts with an image and not the entire object? 

Tia
Use vertex groups. Select the vertices you want to displace, then go to "object data properties" in the properties tab, and create a vertex group. Assign your selected vertices to the group, then under the displacement modifier, choose your group in the box were it says "vertex group".