What is a Camera’s Shutter?

Similar to household shutters, which lets light into a room or shuts it out, a camera’s shutter prevents light from entering the exposure chamber. Inside the exposure chamber is light-sensitive film or electronic sensors that capture the light when the shutter is opened.

The shutter opens and closes for a preset length of time. If the light is bright, the shutter opens and closes quickly. If the light is low, or dim, the shutter must open and close more slowly to allow more of it into the exposure chamber.

Think of the human eyelid as a shutter. It opens, it closes. When it’s closed, light does not enter. When it opens, light enters, and is recorded as images on the brain’s photosensitive “electronics” and our brains see images. When we walk out of a darkened movie theater into bright summer daylight we blink, we squint; our “shutters” try to shut the light out.

On cameras with shutter speed control, the shutter speed can be changed from open for as long as the shutter button is depressed (“B”), to as quickly as 1/8000^th of a second on more advanced cameras.

Single Lens Reflex (SLR) cameras have a dial with shutter speeds indicated, such as: 1 (one second), 2 (1/2 second), 4 (1/4 second), 8 (1/8 second) 15, 30, 60, 125, 250, 500, 1000, 2000, etc, all fractions of a second. Thus, a shutter speed of 2000 (1/2000 of a second) will open and close quickly.

 

Single Lens Reflex shutter speed dial (left), digital camera “mode” dial (right).

The sole purpose of shutter speeds is to control–over a period of time–how long the light-sensitive film/digital receptors are exposed to the image it “sees” through the shutter.

IMPORTANT: Each shutter speed shown on a film camera dial (above left) allows double, or half, the amount of light as the shutter speed above or below it. With only two exceptions everything doubles or halves with shutter speed on a manually set film camera. (Digitals don’t quite follow this rule.)

So why aren't we given only one shutter speed?

Because sometimes a photographer wants blur. Sometimes the photographer wants stopped or “frozen” action. Above all, and of first importance, the photographer wants a properly exposed photograph. A bright sunny day will require a faster shutter speed than will a dim rainy day or when the sun has set below the horizon.

 

Same scene, same action, same lighting, different shutter speeds.
The shutter opened and closed much more quickly for the photo
on the left (1/500 of a second). In the photo on the right the shutter
opened and closed more slowly. During the time that the shutter was
open the person moved through the scene and blurred. (1/30 of a second.)

 

Slow (long) shutter speed–

The camera was stabilized on a tripod so it would not move.
The carnival rides moved during a two-minute exposure,
but not the entire scene moved. The center lights and the
structure of the mechanisms did not move. The blue bands
are lights on the ride blurring as they whirled around their orbit.
The green bands are lights of a Ferris Wheel blurring as they
circled in their spinning. This photograph would not be possible
if a shutter speed of 1/60^th of a second were used.
It is the domain of a photographer to “see,” to imagine ahead
of time what might/could happen if a shutter speed is slowed down.

 

Fast shutter speed–

A fast shutter speed was used for this photo (1/500 of a second).
The boy leaped into the air as the snow tubers passed beneath.
This photograph would not have been possible with a slow shutter speed;
the airborne figure would’ve been blurred and the immediacy of the scene,
the urgency of his leap would not have communicated the action.

 

Camera movement. Everything in the image is blurred,
an indicator that the camera was jostled or jiggled and
not held stable when the shutter was tripped. This is not
a focus problem, because everything in the photo is blurred.

Intentional, or expected, blur–

As with the carnival ride example above, not all blur is bad. Sometimes it works to the photographer’s advantage, such as “panning” the camera with a moving target. When the camera has a slow shutter speed and the subject of the photograph is moving at the same speed as the camera is pointed, the results can lend a sense of urgency, of dynamic and graphic expression.

Panning with a moving object. In this example the bicyclist moved past
at rapid speed. The camera’s shutter was set at 1/13^th of a second. I preset the focus
on the location where the cyclist would pass, then watched through the viewfinder as
the cyclist approached, moving the camera at the same speed as the rider. When
the cyclist got to her closest distance to me I pressed the shutter.

 

Holding the camera steady–

Take a slow breath, let it out, breathe in until the lungs are half full, and squeeze the shutter button. It takes practice. And, it takes more practice. Do not stab the shutter button, compress it. Then count to “two” before you lower the camera. Practicing this tells your mind that you’re in no hurry. It works.

Sometimes the light will be so poor that you will need a tripod to steady the camera. If you don’t have a tripod, set the camera on the hood of your car or on a tree stump, anything to let the camera “sit” while the photo is taken.

Activity:

Shoot a whole roll of film, or two, or fill up a digital picture card playing with shutter speeds. Experiment with fast shutter speeds and slow shutter speeds. Watch what happens when you stabilize the camera and take photos in low light. Find a fast-moving bicyclist and take a photo with a slow shutter speed. Ask a friend to wave his/her arms in the air and jump up and down while you take photos of the event. Try slow shutter speeds and fast shutter speeds and see what happens with the results. Play and have fun and laugh with the fun you create, or even think you may be originating.