Modern Classic SLR Series
Canon A-1 - Camera Operation
- Part V


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Shutter-Speed Priority vs. Aperture Priority Although most modern SLR cameras has both AE modes as standard feature but this was indeed a hot debate since the '70. The world's first SLR camera to incorporate both auto exposure modes was the Minolta XD-7 in 1976. But the Canon A-1 featured here was introduced a year later in 1977. However, the A-1 was a quantum leap in exposure controls - Other than both shutter and aperture priority, it also has Program AE which was lacked in the XD-7. Having now read how to control the camera for shutter-speed priority and aperture priority AE photography in earlier pages, you might well wonder when it is best to use which mode. Basically, it depends upon what you want your photograph to portray. Shutter speeds are most effectively used to freeze or emphasize movement. The shutter speed priority AE mode is also applicable to most photographic situations. Most people only inter-relate that to action type of photography which is not true all the time. But Canon market and projected that way all those years. If you get more familiar with photography, you will understand it is virtually the same for both method of control. It is essentially more to individual preference and the particular type of photography you are engaging. Aperture priority is most applicable to still photography such as portraiture and landscape photography in which depth of field is an important factor. Some of the best creative commercial and architectural photographs are taken in the aperture priority AE mode. But since many of the older accessories designed for the A Series cameras were still less flexible, this, however, does not apply to some particular fields of photography as close-ups and photomicrography when you are coupling the camera to those accessories that require extension. In this case, you should refer to the section entitled STOPPED-DOWN AE for the Canon A-1.

Selecting a Shutter Speed
The table below can be used as a general guide in selecting an appropriate shutter speed according to lighting conditions when using a standard 50mm lens and 100 ASA film.


Shutter Speed


1/30 to 1/60


l/l25 to 1/250

Mid-summer Beach or Snow-covered Mountains

1/500 to 1/1000

Note: This table is just a general guide and does not necessarily apply when using a lens of a different focal length. If you are using a telephoto lens, for instance, any subject movement and the least bit of camera shake can have a magnified effect on image sharpness. For a telephoto it is necessary to use faster shutter speeds than with a standard lens under the same lighting conditions. It is generally said that, for sharp image results in hand-held shooting,the minimum shutter speed should be equal to or faster than 1 divided by the focal length ot the lens. This means that for a 100mm lens, the shutter speed should be at least 1/125 sec.; for a 200mm lens, it should be at least 1/250 sec.

There are other considerations in the selection of shutter speed. You can usually freeze the action of relatively slowly moving subject or traffic at a shutter speed of 1/250 sec. The same is not necessarily true of a rapidly moving object. Instead of freezing the action, you may want to emphasize it by blurring some part of the picture.

For instance, you could blur a moving subject with a relatively slow shutter speed. Or, using a panning technique, turning the upper part of your body to follow the subject's movement, at a relatively slow shutter speed of perhaps 1/30 sec., you can blur the background to stress the movement. In this last technique, it is best to continue panning as you release the shutter. The direction of movement should also be considered. A subject moving directly acros~s in front of the camera will be blurred to a greater degree than a subject which is moving diagonally across or is heading straight for or away from the camera and may require faster shutter speeds than you would use considering speed of movement alone.

Selecting an Aperture A discussion of how to select an appropriate aperture boils down to an explanation of depth of field. When your subject is in focus, there is only a limited range in the foreground and background of the subject which is also in focus. This zone of sharpness is called
depth of field.

When depth of field is important in your picture, it is best to control the aperture directly using the aperture priority AE mode.

Using a small aperture is great for getting sharp overall focus in a landscape or any other type of subject, but shallow depth of field also has its merits. Using a relatively large aperture will make your subject stand out against its surroundings by blurring the background. This is an especially successful technique in portraiture and special effects.

Programmed AE When the AE mode selector is set to Tv and the AT dial turned to "P" on the shutter speed scale, the camera is set for programmed AE. Correct exposure, both aperture and shutter speed, is automatically set by the camera according to the brightness of the subject and a programmed set of combinations of apertures and shutter speeds.

Metering control is done steplessly from a combination of the highest shutter speed and minimum aperture all the way to slower shutter speeds and larger apertures.

Under some circumstances, the camera behaves as if it were set for aperture priority AE. For example, if lighting conditions are so low that an aperture iarger than the maximum aperture of the lens would be necessary, the maximum aperture remams ixed, and the camera's electronic control automatically shifts to slower shutter speeds until the shutter speed is balanced against the aperture for correct exposure. Of course if it shifts to a shutter speed lower than 1/60 sec., it is advisable to use a tripod and a cable release or to switch to flash photography. The advantage of this particular mode is that it takes your mmd completely off exposurd so that you can concentrate on your subject.

Programmed Combinations of Shutter Speed and Aperture in Programmed AE (with ASA 100 film)

    1. indicates programmed combinations when a lens with a maximum aperture of f/2.8 is used.
    2. indicates programmed combinations when a lens with a maximum aperture of f/1.4 is used.

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Meter Coupling Range /AE Coupling Range When using the FD 50mm f/1.4 S.S.C. Iens and ASA 100 film, the built-in exposure meter couples within a range of EV -2 (f/1.4 at 8 sec.) to EV 18 (f/16 at 1/1000 sec.). At given film speeds, the built-in exposure meter couples with the aperture and shutter speed as indicated in the chart below. Outside the couplina range, the camera warns you by flashing the photographic data inside the viewfinder.

Metering at Low Light Levels
With AE coupling all the way down to EV -2 (with ASA 100 film), the A-1 is capable of metering and producing a natural rendition of the light in very dim lighting conditions.

Since EV -2 is practically the lowest light level at which you can even perceive your subject through the viewfinder, you can basically perform AE photography with the A-1 as long as you can see your subject in the viewfinder when using a film with appropriate sensitivity. This means that the A-1 will usually give you a meter reading even in the most adverse of lighting conditions when performing photomacrography and photomicrography in the stopped-down AE mode. What this also means is that you will be using very slow shutter speeds and may be subject to failure of the reciprocity law. The reciprocity law is that relationship between apertures and shutter speeds discussed earlier in which several combinations of the two will give the same exposure value. The trouble with this law is that it may not hold true at slow shutter speeds. More exposure may be necessary. You will find information concerning reciprocity law failure and how to correct it in the data sheet that comes with your film. Correction of reciprocity failure may involve increasing the light level so that higher shutter speeds can be used. Even when following the instructions of the film data sheet, it is advisable to slightly adjust the exposure over several shots to get at least one perfectly exposed image. Be especially on the alert for reciprocity failure when using color reversal (slide) film which has a smaller exposure latitude than black and white or color negative film. Having a smaller exposure latitude means that it is more touchy about exposure error. Incorrect exposure by only 1/2 exposure step may make a noticeable difference in the image results. Reciprocity failure with color film will result in color shifts as well as underexposure and may require corrective filtration as recommended by the film manufacturer.

Viewfinder A less conspicuous, unusual feature of the A-1 is the fact that, unless you are taking a meter reading, the only thing you can see in the bright viewfinder is the viewing area. All other information is eliminated, leaving you undistracted freedom to focus and compose your picture. LED (Light Emitting Diode), first seen in a Fujica was adopted as the primary display medium to handle the moderately complex camera function and various exposure modes.

The A-1 uses the Central Emphasis Metering method of exposure measurement which reads the entire viewing area with emphasis on the central portion where the subject is most likely to be placed. This metering system ensures correct exposure even when skylight is present in your picture. This camera is equipped with a split-image/ microprism rangefinder focusing screen. There are 9 other type of focusing screens available for individual needs. However, un-like the focusing screen designed for the AE-1 Program in 1981 which permits user interchangeable, the focusing screen of the A-1 would require an experienced technician or factory serviceman to change them for you.

Viewing and Focusing To focus, rotate the focusing ring of the lens as you view the subject through the viewfinder. Do not swing your upper body backward and forward as you focus. The focusing screen is composed of three different focusing aids: a microprism ring and a split-image rangefinder in the central area, and a surrounding matte screen. The split-image rangefinder tells you that the image is "in focus" when the image divided horizontally in half merges to become one complete image. The microprism rangefinder presents a clear, steady image when in focus but a broken, shimmering image when not accurately in focus. When the entire image in the viewfinder is sharp, you know that the focus is correctly set. You can focus with any of these three focusing aids as you like depending on the subject and your preference.

Optional Viewing Aids

Dioptric Adjustment Lenses S The dioptric adjustment lens S is an accessory which slides into the grooves of the viewfinder eyepiece from above to correct individual eyesight. With them, eyeglass wearers can photograph without glasses. The A-l's eyepiece has a standard dioptric adjustment of -1 for normal eyesight. The following 10 kinds of dioptric adjustment lenses are optional accessories:

Eyepiece.jpg (4k)

Dioptor.jpg (3k)

+3, +2, +1 .5, +1, +0.5, 0, -0.5, -2, -3 and -4 (diopters).

The specified diopters of these lenses are recorded as the real power when attached to the camera, reflecting the -1 power of the camera's viewfinder.       
You could select the appropriate dioptric lens by choosing the one closest to the number of diopters in your glasses prescription. But, we propose that you actually look through the viewfinder after placing the dioptric lens over the eyepiece to be sure you have the best one.

Angle Finders A2 and B There are some types of photographic subjects for which viewing them through the eye-level viewfinder of the camera is uncomfortable. This is particularly true in the fields of copying, close-ups, photomacrography and photomicrography. Then it might be more convenient to mount one of these angle finders over the camera's eyepiece. Both angle finders rotate 90 for comfortable viewing from above, below or from the side.

rightangleUP.jpg (6k)
Angle Finder A2 gives a correct image top-to-bottom but reversed left-to-right while the more sophisticated Angle Finder B gives a completely normal image. Both show the entire field of view as well as viewfinder information.

Magnifier S
Rightangleup.jpg (5k) Rightangleup.jpg (7k)
The Magnifier S inserts into the grooves of the viewfinder eyepiece with its adapter to give a 2.5X magnification of the center of the viewing area for precision focusing in close-up work.Its power is adjustable to your eyesight within a range of +4 to 4 diopters. Its adapter is hinged so that the magnifier can be swung upward from the eyepiece after focusing, leaving the entire screen image visible.

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