VIII. ROCK SOLID RELIABILITY
36
Safety Shift
The new evaluative metering algorithm is based on the algorithm for the previous 21-zone
and 35-zone metering systems. With the optimized 63-zone metering sensor and
improved algorithm, more consistent and correct ambient and flash exposures are
obtained with less influence by the subject. The basic concepts for the evaluative
metering algorithm are:
1. Metering is weighted on the linked AF point.
2. If there is a very bright object in the picture, the exposure will be increased.
3. In backlit scenes, the exposure will be increased. With dark backgrounds,
the exposure will be reduced.
The E-TTL II autoflash algorithm uses the newly-developed 63-zone metering sensor.
While based on the previous algorithm which weighted the metering based on the
preflash reading, this algorithm has been further improved to obtain consistent flash
exposures. The major improvements are:
1. Correct flash exposures are obtained even with off-center subjects.
2. The incorporation of lens distance information has been optimized to obtain more
accurate flash exposures even with highly reflective backgrounds.
The following metering modes are provided: evaluative, partial, spot, and center-weighted
average (the same as the EOS-1D Mark II
N
). Also, multiple spot metering and AF point-
linked spot metering is possible with C. Fn I -7-1. Partial metering reads approximately
13.5% of the viewfinder and spot metering reads approximately 3.8%. The ISO bracketing
feature has been eliminated because a survey has shown it to be used very infrequently.
The following shooting modes are provided: P, Tv, Av, M, and Bulb (the same as the
EOS-1D Mark II
N
). A convenient and helpful ISO speed safety shift is provided via C.Fn
I -8-2. If the correct exposure cannot be obtained with the P, Tv, or Av mode, the ISO
speed is automatically shifted within ISO 100 - 3200 to obtain the correct exposure.
Safety Shift is a practical feature that is enabled/disabled through C.Fn I-8. 0 disables
the function. 1 enables either a shutter or an aperture preferred shift and 2 enables an
ISO shift. The function makes it less likely that a busy shooter will get caught out as
conditions change rapidly.
* C.Fn I -7-1 enables AF point-linked spot metering.
Evaluative/Center-weighted
average metering
Partial metering
Spot metering
