Canon EOS 20D
(Canon 20D) Digital camera (D-SLR) diagram for partial metering
and Manual Exposure / Operational cheat sheet
Spot / Partial
metering specifications (approx)
Spot covers 9%
of the viewfinder area - 6mm spot diameter
an 18mm lens
11.5 degrees with a 30mm normal lens
6.2 degrees with a 55mm lens
1 degree with a 344mm lens
What is a Partial Meter?
A Partial Meter is a less accurate type of spot meter with an approximate angle of measure (acceptance)
of about 7° to 13°. The angle of some Partial Meters (like Canon A2/E, Digital 10D, and 20D that 100% of the light measured passes through the spot circle), can be reduced to fall within the spot metering angles using a telephoto zoom lens (the higher the mm of the lens, the smaller/narrower the angle) . In this case they can be used as a spot meter.