The Shutter

The shutter of a camera is a device which controls the period of time light enters the camera. It blocks the light and prevents exposure until the picture is to be taken. On demand, it slides out of the way for a period of time, and then slides back to stop the exposure.

Shutter speeds are designated in fractions of a second, and can be set with a variety of different controls. On most film cameras, a dial is located on the top of the camera which sets the the shutter speed mechanically. On digital cameras the shutter may be controlled electronically through a thumbwheel or command dial, or through a menu.

Every camera has a range of shutters speeds from about 2 seconds up to 1/4000 of a second, depending on the performance characteristics of the shutter. Which of the available shutter speeds you can use depends on several other factors; the range of available apertures, the ISO setting of the camera, and the available light.

Which shutter speed you should use depends on the effect you are trying to achieve, which will vary depending on the movement of the camera, the subject or both.

Motion blur is an effective means of expressing movement in a photo. It occurs when the movement of the camera or subject is recorded over time by using a slow shutter speed. You can pan on a moving subject, keeping it relatively sharp while blurring the background for separation, or you can hold the camera stationary and let the subject’s movement tell the story. You can photograph a moving stream or a body of water and soften it with a longer than necessary exposure.

The ability to freeze motion can be a powerful way of capturing the moment. It also assures the sharpest possible image, which relies on the ability of the shutter to eliminate any movement of the camera.

• 30 seconds — The lower limit of typical Digital SLRs. Usable for digital pinhole or infrared work.

• 4-15 seconds — The lower limit of typical compact or bridge digital cameras. Usable for digital pinhole or infrared work.

• 1-2 seconds — The lower limit of most mechanical shutter 35mm SLRs. Useable for 35mm or digital pinhole photography under bright lighting conditions. Usable for digital infrared work.

• 1/15-1/2 second — These speeds allow existing light photography under dim lighting conditions. They also allow you to soften the flow of a moving stream or waterfall. Usable for digital infrared work under bright conditions.

• 1/30 second — About the slowest shutter speed for hand-held use with a wide-angle lens. Usable for digital infrared work under bright conditions.

• 1/60 second — This is a good general purpose shutter speed, usually the lower limit for handheld use with a normal lens, and a setting most often associated with indoor or flash photography.

• 1/125 second — This is a fairly worry-free speed when using standard zoom lenses.

• 1/250 second — This is usually the maximum speed at which you can sync to a flash.

• 1/500 second — Good for use in bright sunlight, or with most telephoto lenses.

• 1/1000-1/4000 second — These speeds allow the photographer to freeze motion, such as in sports.

Shutter speed plays a minimal role in flash photography. As long as the shutter remains open for the duration of the flash, it does not affect the exposure significantly. However, many cameras have a “slow sync” feature which allows some ambient light to influence the exposure. Also known as “fill flash” this can help to achieve a more natural exposure while reducing the dark shadows created with backlit scenes.

Automatic exposure cameras that have a Shutter Priority mode allow the user to select a shutter speed, while the camera selects the corresponding aperture speed for the proper or desired exposure. This allows for more predictable results when shooting in low light.