Canon EOS 1DS MARK II 9443A009 Instruction Manual (en)

Ec-series Interchangeable Focusing Screens
Ec-A: Standard microprism
Ec-H: Laser-matte with scale
Ec-B: New split screen
Ec-I: Laser-matte with cross hair
Ec-CII: All Laser-matte
Ec-L: Cross split screen
Ec-CIII: Laser-matte
Ec-N: New Laser-matte
Ec-D: Laser-matte with grid
Ec-R: New Laser-matte
If you do not change the focusing screen that came with the camera, you 
need not change C.Fn-00-1 factory setting. 
To change the focusing screen, refer to the instructions that came with 
the focusing screen. 
The Ec-A, Ec-B, Ec-I, and Ec-L focusing screens have a prism at the 
center. A correct exposure reading cannot be obtained with evaluative 
metering or spot metering based on the center area where there is a 
prism. Use centerweighted averaged metering or off-center spot 
metering with such focusing screens.