Material ID layer problem

[grabuge]

Hello everyone,

I'm kind of new to vray and I find it great so far. I'm used to artlantis that allows rendering a material ID layer as well. But my problem is this : the material id rendered by vray is kind of blurry and it makes it really hard to work on it with photoshop, since every material ID has a huge color range on the sides. In artlantis every single pixel has the right color attached to a material.
Is there a way to have a clean material ID layer ?

Thank you