Canon AE-1 Film Camera Instructions
- June 3, 2024
- Canon
Table of Contents
Canon AE-1 Film Camera
Canon’s newest SLR, the AE-1, follows the booming trend toward smaller,
lighter SLR’s. What’s the secret for packaging a full complement of features
into such a tiny, fully automatic camera? Basically, it’s mechanical
simplicity combined with ingenious electronic design.
At first glance, you might think of the AE-1 as a scaled-down Canon E F. Like
the EF, the AE-1 provides fully automatic diaphragm control using the FD
series of lenses. You set the electronically controlled shutter speed you
want -the camera sets the f /stop. And both cameras use a single si I icon
photocel I requiring DC amplification. But that’s where the similarity ends.
The innovative approaches in the AE- 1 may point the way to future camera
designs in several areas. For one thing, there’s the unique memory circuit.
Canon engineers, it seems, decided the memory-capacitor system for
remembering the exposure data was old-hatnot sufficiently stable. Olympus
felt that way too when they designed the OM-2. The Olympus OM-2 eliminates the
memory capacitor by taking its reading after the mirror rises (from the
opening curtain for fast speeds and from the film for slow speeds). But the
Canon AE-1 takes a different approach -it uses a digital logic circuit to
memorize the exposure data.
Since Canon also manufactures pocket calculators, perhaps it’s not so
surprising to find this type of circuitry in their AE-1. You may recall the
first installment of our current series of Craftsman articles on digital
electronics -there, we indicated it wouldn’t be long before you’d be seeing
these circuits in cameras. If you’re working on an AE-1, that moment has
arrived.
Pushing the release button tells the bistable flip-flop to start counting. The flip-flop counts until a comparator circuit shuts it off. The comparator sees the light conditions, film speed, and shutter speed as one input. At the other input, it sees the output of the flip-flop- a binary count which has gone through a digital-to-analog converter to become a voltage level.
Most of the AE-1’s components mount to the flexible circuit board. Three /Cs
dominate the circuitone on each side of the pentaprism and one above
the eyepiece. Canon has literally put a computer on a chip a micro processing
system using large-scale integration ( LSI) which handles just about all the
camera’s functions.
Figure. 1
Figure 2
A single 6-volt silver-oxide battery powers all the electronic-control circuits. The battery-test button has a dual purpose- it also serves to cancel any other function by depriving the circuits of power.
Most electronically controlled cameras use one
electromagnet- the AE-1 has three. You can see two of the magnets after
removing the MIRROR RELEASE bottom plate. The
electromagnet on the wind-lever side controls the closing curtain. And the
combination magnet (permanent magnet plus electromagnet) on the other side
releases the mirror.
When these two voltage inputs are equal, the comparator shuts off the
flipflop. The flip-flop then stores-or “remembers” -the count as long as it
has operating power.
Precisely 10 ms later, the mirror releases. Here again, the AE-1 takes a novel
approach-an electronic circuit releases the mirror. When you cock the shutter,
a lever running across the bottom of the camera pushes an armature against a
permanent magnet. The permanent magnet now holds the armature, consuming no
battery power. But there’s a coil of wire wound around the permanent magnet-
that makes the permanent magnet a “combination” magnet. So, 10 ms after the
flip-flop starts counting, a control circuit sends a spurt of current through
the coil. The coil develops a field that opposes the field of the permanent
magnet. And the permanent magnet, temporarily disabled, releases the
armature. Now, the spring-loaded armature shoots toward the front of the
camera and releases the mirror. As the mirror nears the taking position, it
releases the opening curtain. There’s nothing unusual about that part of the
operation – the shutter is a conventional doubleroller design. But while the
mirror is moving up, the AE-1 automatically sets the diaphragm opening to the
f/stop decided by the memory circuit. And here the ope,ation is unique.
In the Canon E F, a trap-needle ar
rangement controls the diaphragm clos- Figure 4
Diaphragm-control mechanism on the side of the mirror cage. Notice that the
stop pawl is engaged with the ratchet gear-that’s what stops the diaphragm at
the right f/stop. Figure 5
The Speedlite 155A may look like any other series-thyristor flash providing a
choice between two f/stops. But mated to the A E-1, it does a lot more-it
automatically sets the diaphragm opening and the shutter speed. And there’s a
not-so-obvious touch of sophistication in the way the Speedlight 155A fires
the trigger capacitor-it uses another SC R. So the 300 volts stored in the
trigger capacitor doesn’t appear across the shutter’s sync contacts. ure. Not
so in the AE-1. In the AE-1, an electronic circuit senses how far the
diaphragm has closed. When the diaphragm reaches the proper aperture, the
circuit shut!: off the current to another magnet-an electromagnet located on
the bottom of the mirror cage.
The energized diaphragm-control electromagnet holds its armature to keep a
pawl disengaged from a ratchet gear (you can see the pawl and the gear in the
illustration showing the side of the mirror cage). As long as the pawl clears
the gear, the spring-loaded diaphragm can close. All the electronic circuit
needs to know is how far the diaphragm has stopped down. When the diaphragm
reaches the proper aperture, the circuit de-energizes the diaphragm control
electromagnet. And the pawl drops into engagement with the ratchet gear to
stop the diaphragm action.
A resistor board mounted to the side of the mirror cage senses the
diaphragm’s position. The wiper for the resistor couples to the diaphragm in
the lens. So, as the diaphragm closes, it moves the wiper along the resistance
path. Another comparator circuit sees the resistance value at one of its
inputs.
This comparator also sees the information stored by the memory circuit at the
same input. So it adds these two values and compares them to a fixed
reference voltage at the other input. When both inputs are equal, the
comparator shuts off the current to the diaphragm-control electromagnet.
Since the AE-1 electronically governs the aperture, the galvanometer plays no
role in setting the exposure. That’s in contrast to the E F where the position
of the galvanometer needle determines the actual f/stop. In the AE-1, the
galvanometer serves strictly as an indicatorid tells you what f/stop the
camera will automatically program. You can also set manual f/stops. Here, the
diaphragm-control electromagnet remains energized. And the diaphragm stops
down to the aperture you’ve selected. When you’re set to a manual f/stop,
Canon makes sure you know about it-a flashing LED illuminates the letter “M”
on the focusing screen as you start depressing the release button. Another
flashing LED in the viewfinder warns of underexposure -not enough light for
proper exposure. With all those indicators, it’s pretty tough to make a
mistake.
The electromagnetic release lends itself to another unique feature of the
AE-1 -an electronically controlled self timer. The self-timer lever sits next
to the release button. Pushing the self-timer lever forward closes a switch
which delays the release of the mirror for 10 seconds.
So there’s only one change in the circuit operation-the circuit waits 10
seconds (rather than 10 milliseconds) to send a pulse of current through the
coil of the mirror-release magnet.
Since there’s no familiar buzz of a gear train, how do you know when the self
timer is in action? As you might expect, another flashing LED signals the
self-timer operation. Moving the self Timer lever toward uncovers the LED on
the top-cover plate. If you count the LED pulses, you know how much time you
have before the shutter releases the LED flashes on and off twice a second.
So far, we’ve mentioned two magnets in the AE-1-the one that releases the
mirror and the one that controls the diaphragm. There’s one more. The
electromagnet visible from the bottom of the camera on the wind-lever side
controls the release of the closing curtain.
Here, at least, the AE-1 sticks to conventional electronic-shutter control.
Setting the shutter speed selects the resistance value in series with the
timing capacitor. That determines how fast the timing capacitor can charge.
When the timing capacitor reaches a sufficient charge, it shuts off the
current flowing through the closing-curtain electromagnet. And the
electromagnet releases the closing curtain to end the exposure.
SOPHISTICATED ACCESSORIES FOR THE AE-1
One has to marvel at the ingenuity of the Canon engineers in designing the
AE-1. But Canon went even further they introduced a new electronic-flash unit
with comparable sophistication. Used with any other camera, the Speed lite
155A provides typical thyristor control. A phototransistor sees the light
reflected from the subject. So the gain of the phototransistor controls the
charging time of a capacitor. When the timing capacitor reaches a sufficient
charge, it fires one SCR.
Turning on the SCR connects a reverse bias across the series thyristor (the SCR in series with the flashtube). A charge stored in another capacitor reverse biases the series thyristor to shut off the flashtube’s current. Nothing unusual here.
But putting the Speed lite 155A on the AE-1 takes full advantage of the flash
unit’s capabilities. As a team, the AE-1 and the 155A won’t let you make a
mistake. Forget to set the f/stop? No problem The 155A automatically sets the
diaphragm opening. You can’t even set the wrong shutter speed. Regardless of
your shutter-speed setting, the Speed
lite 155A auomatically programs a 1 /60-second exposure.
What happens if you release the shutter before the flash unit has recycled?
If the ready light isn’t on, the Speedlight 155A won’t fire. You’ll get
whatever shutter speed you’ve set on the speed setting dial. And the diaphragm
will stop down according the to the available light conditions.
The Power Winder A provides yet another sophisticated accessory for the AE-1.
Unlike other motor drives, the Power Winder has no release button – you use
the camera’s release button. The Power Winder then automatically cocks the
shutter and advances the film.
By putting part of the motor-drive control inside the AE-1, Canon made the
Power Winder exceptionally compact. The switch that tells the Power The
Power Winder shown here can advance the film as fast as 2fps if you hold the
release button depressed.
Winder when to cock the shutter is inside the camera, operated by the closing curtain. With the Power Winder attached, the AE-1 isn’t much larger than conventional 35mm SLRs.
SERVICING THE AE-1
One thing about this current generation of electronically sophisticated
cameras-they’re here to stay. You can’t overlook them. Electronically
controlled cameras already dominate today’s designs. And as for the future,
we can expect to see the trend continue to grow.
In the case of the AE-1, the electronic sophistication also makes the camera
remarkably inexpensive. The advanced IC technology eliminates around 300 of
the parts you’d expect to see in a camera that does so much. As a result,
Canon really saves on labor costs. And Canon passes on that savings to the
consumer-the AE-1 sells for around $300 (as low as $250 in some places). Put
such a low price-tag on a compact, talented SLR-along with Canon’s fullscale
promotion-and you have a camera that’s selling like wildfire.
All this electronics sophistication does make us more dependent on information from manufacturers and distributors. At one time, a good technician could figure out just about any camera without relying on service manuals. But it would be pretty tough to troubleshoot a camera like the AE-1 without a schematic. Plus, it’s essential to know the factoryspecified voltages and currents at several points-you need that information to make the adjustments.
For example, take a look at the bank of resistors on the side of the AE-1 ‘s
pentaprism. One is for the actual lens opening-you just make the adjustment
until the diaphragm stops down the proper amount for the light conditions. But
to make the other adjustments, you must measure voltages at different points
using a digital voltmeter (nothing else will detect these tiny signals with
the precision needed). Then, you must figure out what those voltages should be
by using the camera’s standard reference voltage as a starting point.
So, in servicing the AE-1, a pocket calculator becomes a handy “special tool.”
Most of the repairs in the AE-1, we’re told, involve replacing components on
the flexible circuit board. It’s normally too time-consuming and too expensive
to replace the complete circuit module. And replacing an IC requires that you
go through the adjustment sequence. Plus, you need a delicate touch with a
soldering iron. Those soldering techniques you’ve been using for years may
not be satisfactory in the AE-1.
Fortunately, there’s a bright side to all this. Armed with the service
information, repairing the AE-1 becomes straightforward. And, when it comes
to distributing service information, Canon does a great job.
Canon started by conducting a series of four-day training sessions for their warranty people. The last of these excellent seminars concluded in February. But Canon hasn’t stopped there. They want to reach the independent service technicians as well.
That’s why Canon is cosponsoring this year’s series of National Camera Area
Workshops covering the AE-1, the Speed lite 155A, and the Power Winder A.
Canon will supply the equipment-National Camera will prepare the training
materials as well as present the programs. As with the factory seminars, the
Workshop sessions take four days. That allows time for adjustments and
troubleshooting.
Both Canon and National Camera realize that the average camera repair
technician isn’t an electronics expert.
But you don’t have to be – that’s a comforting thought. Our thanks to Canon
for their splendid job in disseminating service information through various
channels.
Here are the dates for the 1977 National Camera Area Workshops on the AE-1
photographic system:
Detroit May 11-14 Boston (Peabody, Mass.) May 16-19
Detroit May 11-14
Boston (Peabody, Mass.) May 16-19
Albuquerque June 15-18
Atlanta June 20-23
San Francisco October 11-14
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