Sometimes you have to use negative numbers even if you've reversed it. Depends on black vs white and also what the texture is mapped on. Terrains and ground planes seem to be opposite. I decide whether to reverse the bump in the picture editor soley by looking at the transparency squares in the far right image. Then back in the lab I set bump, get out and do a plop render to see if I have to set the bump to negative. Just part of the process.