Don't use photoshop, or colour correction in 3ds Max on displacement maps. You are simply destroying perfectly normal texture. The correct way of using displacement, is dead simple - load the texture with gamma override = 1.0 (this is very important!!) and use displacement min/max level in Corona material, or in Corona displacement mod. And that's it!! You don't need any level or contrast boosting, since that's simply renders height data incorrect. The only thing you should pay attention at, is where is your displacement texture's mid point - if it's 0,5 grey, then make sure that min and max levels has the same value in Corona displacement.