I believe that you should use a dither of some type and not grayscale. It boils down to how the lasers effect has on the targeted material.
When you use the NTM, it’s only black and white or very little gray. This is because when it gets lased, it does a molecular bond with the Titanium Oxide and the tile. So gray isn’t really feasible. They work very much like a black and white printer or newspaper.
What makes them is to use a dither of some type, I commonly use stucki as a dither.
This is a long thread, but it might enlighten you a bit on this.
Good luck.
