Canon EOS
Rebel XT (Canon 350D) Digital camera (D-SLR) diagram for partial metering
and Manual Exposure / Operational cheat sheet
Partial
Meter area covers about 9%
of the viewfinder area
Partial angle with a 27mm normal lens is about 12.5°
(degrees)
What is a Partial Meter?
A Partial Meter is a less accurate type of spot meter with an approximate
partial angle (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.
Some other
Partial Meters (like low-to-medium-end Canon SLRs/D-SLRs such as Rebels, and
Elans) lack a distinct frame and are difficult to use their Partial Metering
function easily and accurately. Others with a frame (like low-end Nikons
such as N50, N55, N60, and N65) that do not measure 100% of the light going
through them (it is close to 80%) cannot act as an accurate spot meter even
with a long telephoto lens.
When does a Partial
Meter becomes a
Spot Meter?
When a Partial
Meter (such as Canon Rebel XTi) used with a telephoto lens, it could
be used as a narrow-angled Spot Meter.
For example, when a Canon Rebel XTi camera is used with a 70mm lens, then,
the Partial angle (acceptance) is decreased from 9° (degrees) to about 4°
(degrees) matching Nikon D70's spot angle (D70 lacks a distinct spot frame) with a 31mm lens.
Please note that only 100% partial meters (where 100% of the light passing
through the partial/spot circle is measured) with a distinct spot frame
(Rebel XTi lacks the frame) can become a true spot meters when used with a longer
/ telephoto lens.
