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Shutter


Shutter speed can be selected manually by turning the shutter speed dial found on many cameras.
Shutter speed can be selected manually by turning the shutter speed dial found on many cameras.

At its most basic, a shutter is a movable cover for an opening. In photography, that opening is the lens. The shutter blocks the passage of light traveling through the lens to the film or digital sensor when it is closed, and allows light to reach the film/sensor when it is open. The length of time that it is open is called the shutter speed. In other words, shutter speed controls the amount of time the film or sensor is exposed to light. The longer the shutter is open, the more light will reach the film/sensor.

A digital camera may not have a traditional mechanical shutter at all, dependent on the type of sensor it has. The sensor itself may simply be switched on and off for the amount of time needed for light to strike it to make an exposure.

TYPES OF SHUTTER

There are two main types of shutter - the "leaf" or "between-the-lens-shutter," which is built into a lens, and the "focal plane shutter," which is built into the camera body. The focal plane shutter is the most common type, found in consumer cameras and most advanced and professional 35mm systems.

A SHUTTER CONTROLS HOW LONG LIGHT STRIKES THE FILM

Shutter speeds can be measured in hours, minutes, seconds and, most commonly, fractions of a second. They are indicated on a camera - usually on a mechanical dial, a liquid crystal display (LCD) data panel on the camera, or visible in the camera’s viewfinder - by numbers such as 1, 2, 4, 8, 15, 30, 60, 125, 250, 500 and 1000. (Not all cameras have the same range of shutter speeds.)


WHAT DO THE NUMBERS REPRESENT?

The numbers stand for fractions of a second. You are meant to consider the numbers to have a 1/ in front of them. For example, the number 2 shown on a shutter speed dial is actually meant to be taken as 1/2 for a 1/2 -second shutter speed. In a similar manner, 4 is 1/4-second, 60 is 1/60-second and so on up to 1/8000-second. (That’s right - some cameras have a shutter that remains open for 1/8000 of a second, a remarkably fast, action-stopping shutter speed.) The number 1 represents one second.

Common shutter speeds are 1 second, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500 and 1/1000 of a second. When referred to throughout PhotographyTips.com, these speeds are written as 1/4 sec or 1/500 sec, and you may see them written elsewhere in photography literature as 1/2s or 1/250s. Some cameras permit intermediate shutter speeds, such as 1/90 sec.

WHAT IS THE SLOWEST SHUTTER SPEED?

Shutters can be kept open for longer periods than one second, indefinitely in fact. Slow shutter speeds to 10-seconds and sometimes even several minutes can be accurately controlled by some cameras’ electronically-controlled settings.

Too slow a shutter speed makes moving subjects a blur.
Too slow a shutter speed makes moving subjects a blur.

Fast shutter speed and fast film stopped these dancers, practicing an unusual hockey-ballet, in mid-air.
Fast shutter speed and fast film stopped these dancers, practicing an unusual hockey-ballet, in mid-air.

The shutter can also be held open while the photographer times the exposure by using the shutter’s “B” setting. The shutter remains open in the B setting (the "B" stands for "bulb) for as long as the shutter release is pressed down. Such long exposures are commonly called “time exposures.” Usually when slow shutter speeds are written (in your camera’s manual, for instance), they are differentiated from fractional shutter speeds by placing a quotation mark (") after them, so 2" stands for two seconds, and 30" stands for 30 seconds.

THE NEXT SHUTTER SPEED EITHER DOUBLES OR HALVES THE TIME

You will note when going upwards through the range of shutter speeds mentioned above that the numbers reduce by 50% each time. For instance, the numbers 2 and 4, which represent 1/2 and 1/4-second respectively, show that the next-fastest shutter speed after 1/2-second is twice as fast (1/4-second) which allows light to reach the film or digital sensor for only half as long. The entire range of shutter speeds works this way, with the shutter speed settings on both sides of a given speed being either half as fast or twice as fast as that speed. This means when you switch from one shutter speed to the next one, exactly half or twice as much light will strike the film/sensor. It’s important for you to remember this, since the aperture, which works in conjunction with the shutter to control exposure, also has a range of settings that permit half or twice as much light to strike the film/sensor as you change from one aperture setting to the next one.


Changing shutter speed from one setting to the next setting is known as a “one-stop” change. If you decrease the shutter speed from, say, 1/250-second to 1/125-second, you have decreased the exposure by one stop. A two-stop decrease would be to go the next-slowest shutter speed, which is 1/60 second. A two-stop increase in exposure from 1/250-second would bring your shutter speed to 1/1000-second.

WHY ARE THERE DIFFERENT SHUTTER SPEEDS?

Right now, you are probably wondering, “Why does a camera need to have different shutter speeds, anyway?” Good question. It hits right on the mark, because it leads to the most important things you should know about shutter speed.

First, to obtain proper exposure.

In a nutshell, if too much light strikes the film or digital sensor because the shutter speed is so slow that it lets light reach the film/sensor for too long, the film or digital image will be over-exposed - with detail all washed-out. It’s like a brilliant white light just in front of your eyes, washing out everything with whiteness. But, if too little light strikes the film/sensor because the shutter speed was too fast, the film or digital image becomes underexposed, with detail rendered as a darkened jumble of shadows or just plain blackness. So, shutter speed has an important effect on proper exposure.

Very slow shutter speed was used for this time exposure.
Very slow shutter speed was used for this time exposure.

High shutter speed froze the descent of this behemoth.
High shutter speed froze the descent of this behemoth.

But, what else does it do? For instance, why would you want to use a shutter speed as fast as 1/500-second instead of 1/60-second if either one or the other can be used to give proper exposure? Before we answer this (below, where it says "Second"), you should know that you can, in fact, get proper exposure in many photography situations at both of these vastly-different shutter speeds if you change the aperture appropriately when you change from one shutter speed to another. The combination of both aperture and shutter speed determine proper exposure. (See our section on Exposure to learn how this works.)

Second, to show the effects of motion.

At 1/500-second, which is a very fast shutter speed, action can be “frozen.” A running athlete, for instance, will appear stopped in mid-stride. The same athlete, when photographed with a shutter speed of 1/30-second, will appear partially or completely blurry. This means that by selecting a fast shutter speed, you can stop motion and render a moving subject with sharply-defined detail. By selecting a slow shutter speed, you can show the effects of motion by having some blur in your image. Some photographs need the blur while others need crystal clear sharpness to deliver their message.


Third, to minimize camera shake

At slow shutter speeds, the entire image will become a blur if there is any movement of the camera during the exposure. Fast shutter speeds help to minimize the effects of camera shake.

Fourth, to allow you to control depth-of-field.

There is a fourth reason for needing different shutter speeds. Since you must change the aperture setting when you change the shutter speed to retain proper exposure, a change in shutter speed will allow you to select an aperture that provides more or less depth-of-field in your image. We invite you to visit our sections on Aperture and Depth-of-field to learn more.

Opening this camera's back reveals the location of its shutter.
Opening this camera's back reveals the location of its shutter.
Further information...

Releasing the shutter

Slow shutter speed

Slow shutter hand-holding

Shutter speed guide
Related topics...

Daytime long exposure photography