The second is a shutter. Shutter speeds are explained as how long the aperture stays open. It is expressed in fractions of a second. For example, 1/1000 of a second, 1/500 of a second, 1/250 of a second all the way down to whole seconds, which are rarely ever used. The larger the number the faster it opens and closes. The smaller the number, the slower it opens and closes. The longer your shutter stays open, the more light will collect on your image. By the way, some cameras display these fractions with the denominator only (bottom number) such as 1000, 500, 250, etc. Some cameras display both the numerator and the denominator, such as 1/1000, 1/500, 1250, etc.
The functions below are taken from a Nikon Digital SLR camera. Even if you don’t own a Nikon, many of these functions are very similar with most camera brands. I suggest you have your camera while reviewing these functions.
“S” – Represents “Shutter Priority”, NOT “Sports” as some people assume. Shutter Priority means you control the speed of the shutter – how long the shutter stays open. While the shutter is open, it will record anything it sees. When you keep your eyes open, you see continuous movement of objects. If you open and close your eyes very fast, you’ll tend to see a freeze frame of that object. Think of a strobe light in the dark. With a strobe, you don’t see movement, only a collection of still images, even when the subject is moving. Therefore, if you use a slow shutter speed, you can get blurry images for this reason. However, when you use a fast shutter, you can stop action. Generally speaking, you would choose a fast shutter speed for sports, speeding cars, dancing, etc. If you don’t want to freeze action, slow your shutter speed down and you may see the hem of a dancer’s dress moving (or blurring) to communicate movement in your images. This function will allow you to control how much movement you see in an image. Flash can also freeze images under certain circumstances, but that’s another lesson. The other function a slow shutter speed will offer is to pick up ambient light in the background when using flash. Have you ever taken a picture in a church but the background is so dark that no one knew where you were? Go to “S” and slow your shutter down. You’ll find the background begins to develop on your image. Practice dialing in “S” and find an index finger or thumb wheel close by and watch the numbers change. Practice taking the same image with different shutter speeds and observe the differences. In this function, you control the shutter, but the camera will choose the corresponding aperture to achieve a proper exposure.