I have created a tilable skin texture in ZB of which i have exported out as an alpha for bump mapping purposes. I now want to create subtle variations of the same texture to keep my bump maps looking more varied, but when i export the alpha, is seems to change its 'z-ness' for want of a better word. This results is all the alphas having different depths even though they are all small alterations of the main one. How can I 'lock' the alphas so that they all maintain an even depth??