When using your DSLR camera in other than Auto mode, you will need to become familiar with a few concepts that might seem complicated at the beginning, but are a lot simpler than you think. Shutter Speed, Aperture, ISO, White Balance are possibly the most common and also important ones.
Shutter – time to let the light in
The easiest way to understand the concept of Shutter is to think of what it is in its most basic form: a curtain. More like two full curtains, one in front of the other. If you wanted to let some light into your room, you would open the curtains. And if you wanted to let some light into your room for a period of time, well then you would open those curtains for a period of time, and then close the curtains. And those curtains, in a camera, become your Shutter.
Speed – how fast are we opening that Shutter
The amount of time that the Shutter is opened to allow light in to take a picture is referred to as the Shutter Speed. Back in the days of the 19th century, when photography was in its infant first steps, it was not uncommon to have Shutter Speeds of hours, minutes and, later on, a number of seconds. Nowadays, it takes much less time to take a picture, usually measured in fractions of a second.
The vertical Shutter is the most common type of Shutter in DSLR cameras. It is the clever device that allows the photographer, you, to control the total amount of time the Shutter will be open for. It is a pair of vertical curtains, one remains closed and the other is open. When selecting a particular Shutter Speed, for example 1/60th of a second, the closed curtain opens, and 1/60th of a second later, the curtain that was open starts to close. So one curtain opens, and the second curtain closes behind it.
How fast exactly?
Typically the Shutter Speed is measured in fractions of a second, but the actual speed is controlled by the photographer, that is you. Each full speed setting will open the Shutter half the amount of time than the previous one on the scale. This, logically, will let only half the amount of light to come into the back of the camera.
Shutter speeds in a modern DSLR camera will go from a maximum of about 30 seconds to about 1/8000th of a second, depending on the camera, which is pretty fast. There is also, in most DSLR cameras, a Bulb setting that allows the time to be as long as the photographer wants it to be, even minutes or hours (battery permitting).
A typical full stop (half the amount of light) Shutter Speed scale goes a bit like this: …, 4 second, 2 s, 1 s, ½ s, ¼ s, 1/8 s, 1/15 s, 1/30 s, 1/60 s, 1/125 s, 1/250 s, 1/500 s, 1/1000 s, …
Each one being approximately half the amount of time than the previous one, and letting only half the amount of light into the camera.
This scale helps the photographer, you, to decide and control the period of time that light will enter the camera.
The Shutter in your camera is nothing more than a couple of curtains allowing light to come into the camera to the sensor.
The Shutter Speed is the actual amount of time that the photographer allows those curtains to open to let the light into the camera and into the sensor.
A scale of Shutter Speed stops will help the photographer decide and control de amount of time that light comes into the camera. Each full stop value will let in light for half the amount of time than the previous one on the scale.