Exposure Control System - Canon EOS 55 Service Manual

1.3 Exposure Control System
1) Configuration
1. Optics and Sensors
Toe metering sensor which has been vertical
above the eyepiece lens is now horizontal just
above the pentaprism's rear face (with a mirror
as an intermediary) so that it does not
obstruct the Eye-Controlled Autofocus unit.
The same 6-zone metering sensor and 4-zone
Part 2: Technical Information
flash metering sensor as in the EOS 500 /Rebel
Fig. 2-8 Evaluative metering zones
X are used. The 6-zone metering sensor
enables evaluative, partial, and centerweighted averaging metering. Also, with
Speedlite 380EX, developed with the camera, E-ITL flash photography which links
evaluative flash metering to the focusing point is possible. For ITL flash metering,
the 4-zone flash metering sensor is used for off-the-film metering.
2. Metering modes and metering patterns
a. Evaluative metering (Focusing point-linked, 6-zone evaluative metering)
Evaluative metering.uses the same sensor and algorithm as the EOS 500/Rebel
X The three focusing points correspond to metering zones SO, S 1, and S2. Toe
evaluative metering zone is linked
to
the active focusing point. During manual
focus, evaluative metering is always based on the center focusing point. No cor-
rection is provided for differences in horizontal and vertical camera position.
Figure 2-9 shows the metering zones for the respective focusing point and their
weighting. Figure 2-11 shows the sensitivity pattern for each metering zone.
D
Main metering zone
Ill
Intermediate metering zone
- Peripheral metering zone
Fig. 2-9 Metering zones and their weighting
b. Partial metering
With the EOS 500/Rebel X, partial metering with the center metering sensor (SO)
was enabled only with AE lock. However, with the EOS 50 / EL.AN II, partial
metering can be linked to the 6-zone metering sensor's SO, S 1, and S2 zones. In
a Creative Zone mode, you can set the partial metering zone directly with the
metering mode lever.
Normally, partial metering is linked only to the center metering zone. However,
in response to users who want to link partial metering to any focusing point,
Custom Function No. 8 has been provided to enable partial metering to be linked
to the dial- or eye-selected focusing point. (If the focusing point selection is auto-
matic, partial metering is linked to the center focusing point only.)
2-9