Interchanging the Focusing Screen
Compatible with all EF lenses. With slow lenses whose maximum aperture is smaller than f/5.6, the
Ec-CIII: Laser-matte
Suited for photomicrography and astrophotography.
Ec-L: Cross split screen
Compatible with all EF lenses. Focus with the vertical and horizontal splits. Lenses with a maximum aperture smaller than f/5.6 will cause the focusing screen’s split portion to darken.