The size of the aperture determines the amount of light allowed to reach the film. The apertures are indicated by a series of numbers, called f/stops or f-numbers, iV`hich can be found on the aperture ring. The smaller numbers are called large f/stops while the larger numbers are called small f/stops. This is because the smaller numbers represent larger apertures which allow more light to pass through the lens. The largest f/stop on the lens is called the lens maximum aperture; the smallest f/stop the lens minimum aperture. The maximum and minimum apertures differ depending on the lens.

Each time you turn the aperture ring from one f/stop to the next smaller one, the amount of light allowed through is exactly halved. Using f/2 as a standard, the amount of light striking the film will change according to the f/stop indicated below.

How the Aperture Affects the Picture

In addition to controlling the quantity of light, the aperture influences depth of field which, in turn, affects the way a picture will look. When your subject is in focus, there is a certain area in front of and behind it which will also be in focus. This range of sharpness is called depth of field.














Brightness ratio














1. The smaller the aperture, the wider the range of sharpness. This is illustrated by the picture above which was taken at f/22. Compare it with the photo to~s right. This extended depth of field is especially good for such subjects as landscapes.

2. The larger the aperture, the narrower the range of sharpness. An aperture of f/1.4, for instance, can isolate your subject from its surroundings. This is often used to blur a disturbing background in portraiture.

Depth of field is also greater the shorter the focal length of the lens. A 24mm lens, for example, will show greater depth of field than a 50mm lens, provided the aperture and shooting distance are the same. Depth of field is also greater the longer the shooting distance, and is generally greater in the background than in the foreground by a ratio of two to one.

See p. 62 for procedures on checking depth of field.

Exposure Modes

The New Canon F-1 is basically a manual-exposure camera capable of through-the-iens, full-aperture metering and stopped-down metering with the Eye-Level Finder FN. It can be converted to automatic exposure (AE) simply by attaching the suitable AE accessory, such as the AE Finder FN for aperture-priority AE, or the AE Power Winder FN or AE Motor Drive FN for shutter-priority AE. Manual exposure is still possible with one or both of these accessories attached.

The following exposure modes are possible with the New Canon F-1:

1. Match-needle Metering

2. Shutter-priority AE

3. Aperture-priority AE

4. Stopped-down (Fixed-index) Metering

5. Stopped-down AE

Detailed information of these modes is provided in the sections entitled "Eye-Level Finder FN," "AE Finder FN," and "Shutter-priority AE."

I. Full-aperture Metering

With a Canon FD lens, metering is done with the lens at maximum aperture. This is called "full-aperture metering." The lens diaphragm does not close down until the shutter is released. Afterwards, it reopens automatically to the maximum aperture. One of the primary advantages of full-aperture metering is that you are able to view and meter the subject with the viewfinder at its brightest.

1. Match-needle Metering

Set the desired shutter speed and turn the lens' aperture ring until the meter needle bisects the aperture ring. The position of the meter needle is determined by the film speed, shutter speed and the lighting conditions. This manual mode is suitable for virtually all subjects.

2. Shutter-priority AE

Set the desired shutter speed and the camera automatically selects the proper aperture according to lighting conditions. This AE mode is suitable for most subjects but especially useful in action photography.

[For this mode. the AE Power Winder FN or AE Motor Drive FN must be attached to the camera and the lens set to the "A" mark.]

3. Aperture-priority AE

Set the lens to the desired aperture and the camera automatically selects the proper shutter speed according to the lighting conditions. This AE mode ~is useful for portraiture and still photography such as landscapes where depth of field is of importance.

[For this mode, the AE Finder FN must be attached to the camera and the shutter dial set to "A"]

II. Stopped-down Metering

Stopped-down metering is necessary whenever you are using a non-FD lens, such as the Reflex 500mm, which has a fixed aperture, the TS 35mm lens or any of the older FL lenses. It is also necessary whenever you insert accessories which do not have a full-aperture signal pin, such as bellows or extension tubes, between the camera body and lens. Stoppeddown metering is possible, though unnecessary, with an FD lens. For correct exposure, set an aperture smaller than f/2.8.

For stopped-down metering, the lens diaphragm must be closed down (stopped down) to the working aperture. Since the diaphragm will open and close as you turn the lens'aperture ring, depth of field can be easily checked.

1. Stopped-down (Fixed-index) Metering

Set an aperture and unlock the stop-down slide by pushing it in and then releasing it. Turn the shutter dial (or aperturering) until.the meter needle is in line with the stopped-down metering index.

2. Stopped-down AE

Set an aperture and unlock the stop-down slide by pushing it in and then releasing it. The camera will automatically select the proper shutter speed for the lighting conditions.

This AE mode is especially advantageous in such fields as photomacrography and photom~crography.

[For this mode, the AE Finder FN must be attached to the camera and the shutter dial on "A."]

Meter Mode Selector

There are three ways to turn on the meter, each designed to suit particular metering requirements. To set a meter mode, simply turn the mode selector so that its index aligns with the desired setting.


The meter turns on only while the shutter button is pressed halfway (except for "B" and " S " settings on the shutter dial). This mode is suited for AE photography.


The meter turns on the moment you press the shutter button halfway and stays on for 16 seconds even if you remove your finger from the shutter b'utton. It automatically turns off after the specified time, thus conserving battery power. This mode is particularly suited for manual exposure and any situation in which you need more time to meter.


As on "HOLD," the meter, once activated, stays on for 16 seconds even if you remove your finger from the shutter button. In addition, the aperture scale in the viewfinder is illuminated for the same period of time. This mode allows you to meter in low-light situations.

In the "HOLD" and "LIGHT" modes, you can cancel the meter reading any time within the 16 seconds simply by pressing the battery check button. Each mode-ids also cancelled when the shutter is released. If you have turned on the meter on the "LIGHT" setting and wish to cancel only the illumination, turn the mode selector to "HOLD" or "NORMAL." The meter will continue to read, automatically turning off after 16 seconds.


With the AE Finder FN attached and the shutter dial set to "A," a different scale than that used for match-needle metering displays exposure information for aperture-priority and stopped-down AK. Consequently, there is no display illumination in the "LIGHT" mode when the shutter dial is on "A."

| Back to Content Page |