Loss details from texture from painting, texture from masking

Laurelion

As title, it’s since quite time that I have this particular issue. When I try to create and export a textur map from my cavity map, made with masking, instead of this:

I have this:


Now, the funny thing is that if I put in morph UW mode I don’t have any loss of details:


So, teoreticaly it's possibile to have a texture with my UV with this level of details but since it's quite a nightmare have the right scale trying to "export" the image from the morph UV, somebody did knows how extract this texture without loss of details and whit the right proportions?

Thank you very much and sorry for my broken english