Circuit Explanations; Overall Operation - Canon EOS 55 Service Manual

Part 2: Technical Information
2. CIRCUIT EXPLANATIONS
2.1 Overall Operation
1) Shutter Release Button
The shutter button has two detents. At the first, (SWl). autofocusing (including Eye-
Controlled Autofocusing) and metering are activated. At the second, (SW2). the shut-
ter is released.
Like the EOS 5/ A2E, the shutter release time lag is constant to stabilize the mirror
reflex time. The time period from when the motor is turned on to when the front-
curtain magnet releases is fixed at 80 ms.
2) Operation Sequence
Figure 2-20 shows the timing chart. Figures 2-21 and 2-22 show the overall opera-
tion and sequence flow for One-shot AF and Al Servo AF.
Battery check,
Mirror up, Aperture
stop down
Sutter button
pressed 1/2
Motor
EMO
Mirror
Date
Mg3-1
Mg3-2
CN2
Film
Start
Exposure Time
Aperture opens, mirror down, mirror, shutter
charge, film winding
Reverse
100
200 300 400
Aperture closes,
mirror u
Normal
500
Fig. 2-20 Overall Timing Chart
2-26
Subsequent exposures
n
Normal
600 700