Control lightening area
Light like Halogen, CDM and LED can easily be control by their relatively small emitting area if we want to control the area of lightning.
Although using long lampshade and four leaf shade are one of the control methods, we can also use baffle and lens to reach higher accuracy.
Function of baffle just like grille, more and more number of grille make the accuracy of control better. It is because of the light scattering which go through from grille is block by grille.