Canon Focusing Screen EF-S for EOS 40D, 50D SLR Camera

Exclusively for the EOS 40D, this focus screen is optimized for wide-aperture lenses from f/1.8 to f/2.8. Areas that are slightly out of focus appear more out of focus, making it easier to tell when focus is right-on. Ideal for users who frequently manually-focus in dim light with fast lenses.