Canon C12-8453, Service Manual

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2) Processing
The algorithm for automatic focusing point selection is based on the EOS
300/Rebel 2000/EOS Kiss III's. The algorithm increases the chances of selecting
the focusing point that the user wants. For details on the algorithm, see the EOS
300/Rebel 2000/EOS Kiss III's Service Manual.
[Automatic selection mode + Eye Control ON]
In the Full Auto mode (automatic focusing point
selection) while Eye Control is ON, the algorithm
mentioned above is incorporated in the Eye
Control operation to increase the precision of the
automatic focusing point selection.
When Eye Control is OFF in the EOS ELAN 7 E /
EOS 30 or EOS 300/Rebel 2000/EOS Kiss III,
the automatic focusing point selection algorithm
changes depending on whether the priority
focusing point selection grouping is for the
horizontal or vertical orientation. Only two
patterns are provided. However, when the EOS
ELAN 7 E / EOS 30's Eye Control is ON, a total
of 28 grouping patterns for the horizontal and
vertical orientations are provided based on the
Eye Control information. This increases the chances for the camera to automatically
select the focusing point that the user wants. When the shutter button is pressed
halfway (SW-1 ON), all the focusing points start to focus. The focusing point achieving
focus on the closest subject is A, and the other focusing points achieving focus on other
subjects within a certain distance are set as B or C. Then the grouping pattern selected
to match the eye's position is incorporated and a focusing point in the high-priority
group is used to focus. This algorithm is the same one used in the EOS 300/Rebel
2000/EOS Kiss III.
(4) Predictive AI Servo AF control
As with the EOS-1V, the fundamental objective of AI Servo AF control is to improve
the focus tracking of the subject and the focusing precision. This in turn stabilizes
the film advance speed.
1) AI Servo AF control for the first frame
The EOS ELAN II E / EOS 50 E uses the following sequence: The lens stops
immediately at SW-2 ON, the reflex mirror goes up, the EMD stops down, and the
exposure sequence begins. The EOS ELAN 7 E / EOS 30 improves upon this
sequence: The lens continues to be driven even after SW-2 ON. Then the reflex
mirror goes up, the EMD stops down, the lens drive stops, and the exposure
sequence begins (the mechanical parts and predictive lens are driven
simultaneously). As a result, there is less predictive lens driving (front lens
rotation) up to the start of the exposure. This reduces the error or difference
between the predictive lens position and the actual point of focus. This operation
requires CR123A
×
2 batteries whose remaining battery level is at least half. Or, it
requires BATTERY PACK BP-300 + four size-AA batteries having a full charge. If
the battery voltage is lower than the required level, the following sequence is
executed at SW-2 ON when the lens driving stops: The reflex mirror goes up, the
EMD stops down, and the exposure begins.
Part 2: Technical Information
2-5
Fig. 2-10 Automatic focusing point selection
algorithm in the Full Auto + Eye
Control mode (example)
Horizontal
orientation
Vertical
orientation
Priority 1 Priority 2
Eye position
Priority 1
Priority 2
Eye position
Eye position
Priority 1
Priority 3
Priority 2
Eye position
Priority 2
Priority 3
Priority 1