Laser photographic Imaging or raster engraving is in fact the opposite from relief printing.
It actually takes some of the material away to mark the surface. It is a technique used to build up complete images, such as pictures.
Think of it as a printer, working from left to right down the page. But instead of leaving some ink behind it is now taking off a little layer.
The closer the raster, the more filled in the image will look afterwards.
Photographic images can be saved in different ways: