Modern Classic SLR Series
Canon A-1 - Other Issues Part III

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The Viewfinder with the Alphanumeric LED Display

Viewfinder is a section where camera designers always have put a lot of attention to. What is there in a viewfinder ? We use the viewfinder for focusing and composing a subject of interest. In a mechanical SLR camera, arrangement can be very simple and straight forward because it only need to handle the basic core of information such as aperture value, shutter speed in the form of match needle or slightly more complicated in the form of an viewfinder ready light for flash. (Actually, I would rate highly for Olympus's original solution to their mechanical model, the OM3 and 3Ti's multi-spots metering viewfinder display). Contrary to many people's thinking, I would personally feel a viewfinder should be keep as clean as possible and so as not to distract a photographer's attention. The trouble is, putting too many information in the viewfinder tends to clutter it up, obscuring the original purpose of focusing and composing.
The viewfinder display here in the A-1 is turned on just by either depressing the shutter button halfway or by depressing the Exposure Preview Switch or the Exposure Memory Switch. The display is just below the viewfinder image area. It uses digital characters in the form of red LEDs. The brightness is controlled automatically, so the display is neither too bright nor too dim in respect to the focusing screen.

Note: Compared A-1 viewfinder information display methods used with other SLR models.

Since the A-1's metering is extremely sensitive and its pulse-controlled microelectronis give immediate response, these digital displays would normally change at the slightest variation in brightness or composition. In fact, they'd probably changes so fast that you would have a hard time following them. So, they are designed to change no more often than twice per second, and only in 1/2 increments so that the values remain meaningful. But even thought the displays are stepped, exposure control is not, ensuring correct exposure, always.

The Canon A-1 isn't the first SLR to employ LEDs in the viewfinder (Fujica's ST 901 was the first SLR). The difference in these LEDs, however, was designed so as their brightness changes in four steps according to the brightness of your subject. Which means that they are always easily readable, no matter what the lighting conditions.

Finally, focusing with this viewfinder is a snap due to its brightness and utilization of a split-image/mircoprism focusing screen. With its alphanumeric LED display that can be turned on and off at will (off by means of the Viewfinder Display Lever). Below are explanations of the readout of when you are using each AE mode or operating in manual control.

Camera control of shutter speed and aperture will be displayed steplessly, meaning that any value can be chosen automatically whether or not the value is a marked shutter-speed or f-number. So you will see some highly unusual figures such as 750, 350 etc for shutter speed display or 4.5, 6.7, etc. for aperture value in the viewfinder display panel.

Note: It is difficult to get accustom to such displays, as most of us are used to those 'friendly' figures such as f5.6, f2.8 or 125, 500 or 30.. in this case, to avoid confusion, the display only shows aperture value and shutter speed settings to the nearest half-step and it changes the reading at half-second intervals (See illustration at the top) or slower to give you time to read the display (The reading by mean of a SPC cell near the eyepiece and thus it is not real time). If the scene illumination is changing rapidly, the viewfnder display is either may be both in approximate form and slightly lagged behind in display the chosen settings to the photographer. However, the camera itself responds instantly to changed light values, the difference is just the time delay in display. This is similar to the method use in the Olympus OM2n's real time exposure metering system, the blue cells that hide inside the mirror box are used to provide the photographer an visual guide of the recommended exposure values, although when you execute an exposure process, another meter cell will take over the real time exposure process.

The A-1 Digital Display

Viewfinder Shutter Speed Readout

Viewfinder Aperture Value Readout

Shutter speeds in fractions of a second from 1/1000 to 1/2. Includes full steps such as 1/1000, 1/500, 1/250 and half steps such as 1/750, 1/350, 1/180.


Aperture settings from f-32 to f-1.2 in full steps such as f-32, f-22, f-16 and half steps such as f-27, f-19, f-13.


Shutter Speeds in whole seconds or decimals.
"' means second. 0" 7 = 0.7 second;
= 1 second ; 1" 5 = 1.5 second
Includes full and half steps.

Camera at Dial Settings



Shutter Speed set to 'B'

Special Digital Symbols

Speedlite 155A or 199A installed and ready to flash

Speedlite 155A or 199A installed and ready , shutter speed setting on 'B'

Operator error made in switching back to automatic after viewing depth of field

You must control aperture or shutter manually.

Canon A1 side view

Credit: Image courtesy of Mr. ITYW: WESTERBERG®.<> who is a collector for Canon photo gears t. Image(s) copyright © 2003. All rights reserved. Please respect the visual property of the contributing photographer.

Warning Signals
If you have set something wrong, the camera will cause part of the digital display to blink on and off to warn you. It may appear very complicated, but the logic is fairly simple and obvious once you become acquainted with it you can get used to them and instantly know what has gone wrong. For instance, if you are choosing aperture and the camera is choosing shutter speed, the camera will display a flashing shutter-speed display if it cannot find a speed that matches your selection to provide a theoretical correct exposure. If you set a preferred setting on shutter speed, the camera will flash the aperture display to show incorrect exposure. If the camera is setting both controls, on Programmed AE, it will flash both displays to show incorrect exposure.

Shutter-priority AELED.gif Looking from left to right in the viewfinder, the first four digits represent the shutter speed you have selected. Speeds from 1/2 sec. to 1/1000 sec. are shown as whole numbers, just as they are written on the AT Dial scale. Thus, a shutter speed of 1/125 sec. appears as 125 in the viewfinder. And to avoid confusion at slow shutter speeds, those from 1 to 30 seconds appear together with the second symbol ("). Thus, 15" represents a shutter speed of 15 second. Also, when shooting at bulb, the letters "buLb" will replace the shutter-speed displays, with "M" appearing at the far right. When shooting in the Shutter Priority AE mode, the shutter speed you have selected will remain stationary while the aperture displays will continuously change with changes in light conditions. And in case of over-exposure or under-exposure, the appriopriate aperture value will flash on and off as a warning. In addition, in case you are outside the meter coupling range no matter what shutter speed you select, both displays for shutter speed and aperture will flash.  

Earlier Section on Shutter Priority AE >

Trouble Shooting on Viewfinder Error Signals in Shutter Priority AE Mode

Possible over-exposure
 f-number from f-19 to f-32 may keep flash. Camera metering circuit alerts you the shutter speed selected cannot find an appropriate aperture value on the lens in use (exceeding the minimum aperture value of your lens in use) for a corerect exposure. It also serves to confirm whether the lens in use can be stop down that much. If minimum aperture of lens is larger than flashing aperture, overexposure is indicated, in this case, correct it by changing to faster shutter speed until flashing aperture matches with * minimum aperture of lens.
 Camera chooses large aperture and flashes aperture readout. Switch to a slower shutter speed until display stops flashing.
Light too dim for AE photography - below meter-coupling range.
 Both shutter-speed and aperture readouts flash, Change to film with higher speed; increase light on scene; change to lens with larger maximum aperture.
Light too bright for AE photography - above meter-coupling range.
 Aperture readout flashes even at fastest shutterspeed setting. Correction may be: Change to film with lower speed; decrease light on scene; use ND filter; change to lens with smaller minimum aperture.

If lens minimum aperture is f-32: f-32 is the smallest aperture that can be displayed on the scale, a flashing f-32 may indicate the scne may require smaller f number like f-64 or f-128. Switch to faster shutter speeds until flashing aperture readout changes to f-22. If lens minimum aperture is f-16: Occasionally, f-16 may also flash. Switch the scale to to faster shutter speeds until flashing aperture changes to f-11.


Aperture Priority AE LED.gif Following the four shutter-speed displays are two displays for aperture. This time, the selected aperture will remain stationary while the shutter-speed displays change with the lighting. In situation when possibility of over-or under-exposure, the highest shutter speed and a low one respectively will flash. The speed that flashes for underexposure depends on your lens' speed and the ISO of your film. Moreover, just as with shutter-speed priority, both displays flash if you shoot outside the meter coupling range.

Earlier Section on Aperture Priority AE >

Trouble Shooting on Viewfinder Error Signals in Aperture Priority AE Mode

You choose an aperture on the AT Dial that is larger than the maximum aperture of the lens.
No warning. Lens opens as much as it can. Camera chooses shutter speed for actual lens opening. Exposure is OK. Display shows max, aperture of the lens, rather than aperture on AT Dial.
You choose an aperture on the AT Dial that is smaller than the minimum aperture of the lens.
No warning. Lens closes as much as it can.. Camera chooses shutter speed for aperture on AT Dial, rather than actual shooting aperture. Photo is overexposed. Display shows aperture on AT dial.
 Camera chooses fastest shutter speed and flashes shutter-speed readout. Change to smaller aperture setting.
 Camera chooses slow shutter speed and flashes shutter-speed readout. Change to larger aperture setting
Light too dim for AE photography - below meter-coupling range.
 Both shutter-speed and aperture readouts flash, Change to lens with larger maximum aperture; change to film with higher speed; put more light on scene.
Light too bright for AE photography - above meter-coupling range.
 Shutter-speed readout flashes even at smallest aperture setting. Change to lens with smaller minimum aperture; change to film with lower speed; use ND filter; put iess light on scene.

Programmed AE  In the Programmed AE mode, both shutter-speed and aperture displays change in combination as programmed by the camera. If, however, there is too little light for the maximum aperture of the lens, only shutter-speed display will change, becoming slower and slower until correct exposure is obtained.

And if both displays flash indicating you are outside the meter coupling range, higher speed film or additional artificial illumination like a flash should be considered.

< Earlier Section on Programmed AE >

Trouble Shooting on Viewfinder Error Signals in Programmed AE Mode

Over-exposure or light is too bright for AE photography
 Display flashes both fast shutter speed and the minimum aperture of the lens in use.
Under-exposure or light is too dim/dark for proper AE photography
 Display flashes both slow shutter speed and the maximum aperture of the lens in use.

Electronic Flash AE  

With the Canon dedicated Speedlites 199A, 188A, 177A, 155A, 133A, 533G or 577G attached and turned on, you never have to take your eye from the viewfinder as when the unit becomes fully charged, an "F" will appear in the digital readout. Since shutter speed is automatically set at 1/60 sec., no matter what the setting of the AT Dial (except for "B", this will also be shown in the viewfinder). As far as aperture display is concerned, it depends on the auto working aperture you have selected on the flash unit, possibilities being 2.8, 5.6 or 11 with ISO 100 film. Arrangement of these displays will be as shown below.

Earlier Section on Flash AE >

Trouble Shooting on Viewfinder Error Signals in Electronic Flash AE Mode

You set Aperture Selector on flash to call for aperture larger than maximum aperture of lens on camera.
 Display flashes maximum aperture of lens in use to indicate underexposure. Change Aperture Selector on flash to call for aperture lens can use.
You set Aperture Selector on flash to call for aperture smaller than f-16. Overexposure is possible if lens won't close down that far.
 Aperture requested by Aperture Selector on 155A or 199A will appear in display and numerals will flash on and off. If lens minimum aperture is equal to or smaller than flashing value, exposure will be OK. If lens minimum aperture is larger than flashing value, overexposure will result, Set Aperture Selector on flash unit to an aperture size that can be set on lens.

Stopped-down AE 

Since aperture in this mode is controlled by the aperture ring, the only display shown in the viewfinder is the shutter speed, automatically selected by the camera. Exposure warnings are exactly like those in aperture priority. 1000 will flash for overexposure. And if the display flashes even when the aperture ring is set at its extreme limits, you are outside the meter coupling range.

< Earlier Section on Stopped Down AE >

Trouble Shooting on Viewfinder Error Signals in Stopped Down AE Mode

Camera Stop-Down lever locked in before FD or FL lens mounted on camera or on bellows or extension tubes that preserve automatic aperture such as Bellows FL, Extension Tubes FL, Extension Tubes FD 25 and 50.
No warning. Exposure will be incorrect. Avoid problem by always checking camera body before mounting lens. If you see red dot beside camera Stop-Down Coupling Lever, camera Stop-Down Lever is locked in. Release Stop Down lever before mounting lens.
When switching from any other AE mode to Stopped-Down AE, lens aperture ring is turned away from 'A' before film is advanced for next shot.
No warning. Preview metering and viewing depth of field may be done at wrong aperture because lens will not stop down smaller than shooting aperture for last exposure until film is advanced. This will not cause incorrect exposure because you must advance film before exposing next frame. When you shoot next frame, metering is done again, automatically, and exwsure will be OK.
Intending to switch back to AE, you return lens aperturecontrol ring to 'A' but forget to unlock camera Stop-Down Lever.
Warnings: Viewing screen is dark; display is shutter speed only, Camera will set exposure automatically but lens will remain at minimum aperture. Exposure will be correct if there is enough light, If not, shutter-speed display will flash. This is not recommended and severely strains camera mechanism.

Manual Control 

That is, the aperture the camera would choose is displayed, regardless of what aperture you have selected yourself. It's giving you an exposure recomendation, of course, as to what would normally be the best aperture for proper exposure. In addition, an "M" will also be displayed as a reminder that you are in manual mode.

When controlling the camera manually, the viewfinder displays are just like those of shutter-priority.

Earlier Section on Manual Mode >

(Camera display serves as exposure guide. If you set aperture as shown in display, these warnings and signals will apply.)

 An aperture display from f-19 to f-32 will flash. If you set lens at that aperture, exposure will be OK. If lens minimum aperture is f-32 or f-l6 and camera displays flashing f-32 or f-16, apply same tests described in Shutter-Priority AE section.
 Camera displays large aperture and readout flashes
Light level below meter-coupling range.
 Both shutter-speed and aperture readouts flash.
Light level above meter range.
 Aperture readout flashes even at fastest shutter speed setting.

Error Mark Display  

Six red "E"'s will appear in the finder if you push in the stop-down lever, release it and then return the aperture ring to the "A" mark before taking a picture. This situation could occur, for instance, when checking depth of field in the aperture priority mode.When the error message appears in the viewfinder, shutter button and Film-Advance Lever can be both in-operative. Depressing shutter button partway causes display to show error signal even if display is turned off. Correction is by pushing the multiple exposure lever to the left and throwing the film advance lever.

To view depth of field, you take the lens off 'A' and push in the Stop-Down Lever. Then you un-lock the Stop Down Lever and return the lens to 'A'.

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