The shutter serves one of the most important roles in the camera’s operation. Its a mechanism inside the camera that’s critical in capturing a properly exposed image.
The word “Camera” means “room” in Italian. This is because the first cameras were actually rooms. On the windows of those rooms were shutters. A window shutter allows one to control how much light can come into the room and for what period of time. In many places you can find shutters that still serve this purpose.
The shutter on a modern camera does very much the same thing. It opens to let light enter the camera for a specific period of time.
Historical cameras, or rooms, were once used by artists and were called Camera Obscuras, or Dark Rooms. Camera Obscuras were known to exist in the first century and later became popular as an aid for artists to draw or paint.
In a window of this room there would be a small hole, possibly in some material covering the inside of a shuttered window. Opposite that wall would be the artist with paper or canvas.
When the shutters were open, light rays could travel through the hole and project on the canvas or paper an inverted image of whatever was outside the room. Then, the artist could trace the projection onto their material.
Eventually the window hole was replaced with a lens and this increased the clarity and detail in the projected image. So, you can see how this idea of the camera has evolved to become the little box you make pictures with.
The camera’s shutter, like a window shutter, stays closed in front of your CCD chip so the light sensitive recording media remains in total darkness.
When the shutter release is pushed, the shutter opens to allow a projected image to reach your recording media, either film or a CCD chip. The amount of time it takes for the shutter to open and close is referred to as the shutter speed and is measured in seconds or fractions seconds. In other words, it is the amount of time the projected image remains on your light sensitive media.
These are standard shutter speed numbers and can most likely be found on your camera:
2”, 1”, 2, 4, 8, 15, 30, 60, 125, 250, 500, 1000 and higher.
The first number, 2 with quotation marks, represents 2 seconds. On a DSLR whole seconds are represented with quotation marks. 2” is followed by one second, 1/2, a 1/4, an 8th, a 16th, a 30th and so on. You should remember the pattern and keep in mind that the numbers after 1 are understood to be fractions of a second. You may also have other shutter speeds available on your camera other than the ones listed here.
Most likely you’ll also have a shutter speed represented by a B. This stands for Bulb and on very old cameras was the only shutter speed control on a camera. This setting was used when exposure times were very long and were measured in minutes instead of seconds or fractions of a second. The photographer held a bulb, which was kind of like a small air balloon attached to a tube that went to the shutter mechanism. When squeezed the air pressure opened the camera’s shutter until the bulb was released.
If you look at really old portraits you’ll notice that the eyes of the subjects are a little strange. This is because they were blinking during the long exposure. Many times it was the photographer’s job to redefine the eyes by drawing them in on the print. In family portraits you might also notice that the children’s faces are a bit blurry. This is because the children couldn’t stay still and we see blurriness of that motion in the final image.
On your camera, if you push the shutter release when the shutter is set to B, it will stay open until you release it. Even today the bulb setting allows for a lot of fun when doing very long time exposures. And by the way, you can still buy bulbs.
Notice how each shutter speed relates to the others by a factor of 2. This can help you memorize the numbers. I’ll also point out that there is a relationship between each number and the amount of light the shutter lets into the camera.
This is approximately a factor of two. In other words, a 30th of a second lets in twice the amount of light of a 15th of a second. The difference between one shutter speed and the next is called a “stop”.
Its important to remember that the shutter is the mechanism in every camera that controls HOW LONG the light falls on the film or the CCD. Because of this, one of its functions is to visually express motion in your images. One of the unique ways your personal creativity is expressed in a photograph is by using the shutter. It’s the window of endless possibilities. The shutter is the gate through which light is captured. But before that happens, the light has to capture you.