Camera Shutter, Pictures Taken behind the Lens

Shutter types

Basically, there are two main types of shutter: those that work inside or just behind the lens, known as between lens shutters, including sector shutters; and focal plane shutters, which are positioned close to the film.

Between lens shutters

The between lens shutter closely resembles the aperture and is positioned between the lens elements, near the aperture blades. It is made up of two or more overlapping metal blades. which spring open for the time of the exposure and then close again. These shutters are very light and compact, and can synchronize with flash at all speeds. But between lens shutters have two drawbacks: few work at speeds of over 1/500, and they are costly to produce for cameras with interchangeable lenses. This is because each lens requires its own integral shutter and a separate means to block light from the film when the lens is removed.

Between lens shutters are used mainly on rangefinder 35mm cameras and roll film cameras.

Sector shutters

The sector shutter is used on many cameras with small diameter lenses, such as the pocket 110 and simple viewfinder cameras. It is mounted just behind the lens, and consists of a spring-loaded metal plate which prevents light reaching the film until the shutter release is pressed. There is usually a choice of two speeds, indicated by weather symbols marked on the outside of the camera. The faster speed is used in bright, sunny conditions and the slower one on cloudy days. Some cameras also have a separate setting for flash attachments.

Focal plane shutters

Focal plane shutters are made up of two blinds positioned just in front of the film, with an adjustable gap between them, which follow each other across the film plane. High speeds (up to 1/2000) are obtained by altering the size of the gap between the blinds, and lower speeds (down to 30 seconds) by holding back the second blind after the first has travelled across.

The majority of focal plane shutters are made from rubberized cloth and move horizontally across the film, but they will only permit flash synchronization on speeds up to 160. A growing minority use metal bladed shutters which travel vertically, and can synchronize with flash at speeds to 1 /125, because of the shorter distance the shutter has to cover in a 35mm camera. As a focal plane shutter is mounted inside the camera body, close to the film, it protects the film from light when the lens is changed. Extra lenses do not need their own built-in shutter.

Stopping movement

The shutter can also be used to express movement in different ways. A fast shutter speed will stop or freeze movement and a slow one will register a blurred image of a moving subject. The very short exposure time of a high shutter speed can freeze movement and give a sharp image of a moving subject. The speed needed to stop this movement depends on three things: the speed of the moving subject, the distance between the camera and the subject, and the angle at which it is travelling towards the camera.

The closer the subject is, the higher the shutter speed must be. But a great deal depends on the direction of the movement—something travelling towards the camera photographs more sharply at a lower speed than something moving across the camera’s field of view. As a rough guide, in normal conditions objects moving towards the camera photograph sharply at 1/125; at an oblique angle of, say, 45°, at 1/250; and if they are travelling parallel to the camera, at 1/500.

Expressing movement

But the photographer will not always want to ’stop’ the movement of the subject. A racing car, a running child or someone on a bicycle all involve movement–and the camera can be used to express this.

You can convey the feeling of movement by using a slow shutter speed. However, take care to avoid blurring the whole picture, which can happen with too slow a shutter speed, and resulting camera shake. The background needs to stay sharp to keep the feeling of movement. A trial-and-error guide is to estimate the shutter speed necessary to stop the subject completely and then use the speed one setting slower.

Panning the camera

One of the ways often used to express movement is to pan the camera. This has the effect of keeping the moving subject sharp while blurring the background, giving subject detail plus a strong feeling of speed and motion. To do this the camera follows the path of the subject, keeping pace with its movement. It takes practice and a steady hand.

Stand with your feet apart facing the spot where you intend to take the picture. Without moving your feet, centre the subject in the viewfinder and, as it moves towards you, follow its movement smoothly swinging from the hips. When the subject is directly in front of you, press the shutter but continue to follow through the movement to avoid any possibility of jerking the camera. Try using 1/60 or even 1/30—once the technique is mastered you can use very slow shutter speeds to increase the degree of background blur.

Obviously, you can achieve varying degrees of sharpness and blur by using a range of shutter speeds and these techniques. These combinations can, for instance, blur the feet and arms of a sprinter but register the agony of exhaustion on his face.

Shutter and aperture

Both shutter and aperture control the amount of light reaching the film, but their effects are quite different. The size of the aperture controls the depth of field—how much of the picture will be sharp—while the shutter speed dictates how sharp a moving subject will be. Correct exposure is a combination of shutter speed and aperture setting, but the photographer can select any combination of these settings that adds up to the correct amount of light. For example, if the correct exposure for the photograph of the child is 1/125 at f5.6, the negative will be correctly exposed at either 1/500 at f2.8, or 1/15 at f16. But both these combinations have certain limitations. The photographer nearly always has to choose between a fast shutter -speed to stop a certain movement or a small aperture to give a sharp result from 5m to infinity.

Both combinations can give the correct exposure but produce different pictures. Sometimes it is possible to achieve both a small f stop and high shutter speed in very bright conditions.

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