Shutter and Shutter Speed

Photographers often use shutter speeds to convey or freeze motion

The shutter is complicated mechanism acting like a window shade and is placed either behind the camera lens   or is built into the middle of the lens, next to the aperture.

When you take a picture, it opens briefly and allows you to control the amount of time the light passing through the lens remains in contact with the digital image sensor. It is activated by the camera's release button.

The shutter speed refers to how long it remains open and the usual range of speeds is: 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000 sec .

Except for 1, these time measurements are fractions of a second where each increment either halves or doubles the time of the previous one. If we take 1/60 of a second as an example, then it is half as much exposure time as 1/30 of a second, but about twice as much as 1/125 of a second.

Please note that as the number of the denominator grows larger -
2, 4, 8, 15 etc, the speed actually increases. This means that less
light is allowed to pass through leading to decreased exposure.

The doubling or halving of the the speed settings compliments the aperture f-stop scale in terms of the exposure given to the image. The relationship between aperture and shutter speed is know as reciprocity. What it means practically is that the following combination of settings will give the same exposure of the image:

1/30 of a second at f/11 is the same exposure as
1/60 of a second at f/8 or
1/125 of a second at f/5.6

and this allows you to give correct exposure over a very wide range of brightness conditions as well as to control the depth of field of the image.

In addition to giving correct exposure, the speed setting of the shutter can be used to record motion either as frozen or blurred to give sense of action.

You can return to the exposure section to review how aperture (intensity of light) and shutter speed (time) interrelate and can be put to creative use .

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