Understanding Shutter Speed

There is a mechanical component in cameras called the shutter. It's like a little window that opens and closes when you press the shutter button on your camera. It's function, is to allow a certain amount of light into the camera based on time.

Shutter settings are represented in time. For example, you could have a 15" (15 second) shutter speed or a 1/160 (160th of 1 second) shutter speed.

What effect does shutter speed have on my photos?

Shutter speed will have two main functions to your photographs.

Change the amount of light coming into the camera, based in time.
Add motion blur, or freeze moving objects in place

A slow shutter speed and a fast shutter speed depends on your subject. If your subject is a really fast moving bird, you're going to want to shoot at a high shutter speed. The reason being is that you will likely want to capture the bird in flight, which is a very fast motion. A fast shutter speed will freeze the birds motions in place, and not create and blurriness.

Ask yourself what your desired final result is

Ever get those shaky looking photos? That's from a slow shutter speed. Sometimes a slow shutter speed is desired, and other times it is a necessity.

For example, you may wish to use a slow shutter speed to intentionally show motion in your subject. If you're like me, then maybe you want to show motion in water by shooting at a slower shutter speed.

No Photshop required! This effect is achieved in camera by slowing the shutter speed down

In other cases, you may be required to use a slow shutter speed by seconds. This is called a long exposure and is used when you are photographing of the stars. If you are going to be shooting at a slow shutter speed, you absolutely must have your camera on a tripod, and preferably shooting with a wireless trigger. This is because any slight movement in the camera, even your finger gently pushing on the shutter button, can cause a slight movement which will be evident in the final photograph.

TL;DR

Shutter speed controls the amount of light coming into the camera, based in time
A slow shutter speed will allow more light to come into the camera
A fast shutter speed will allow less light to come into the camera
Shutter speed is represented in fractions of a second - 1/160 = 160th of 1 second
Want to freeze a splash of water so that you can clearly see every single droplet? Use a fast shutter speed.
Want to shoot the stars, or write your name with a sparkler? Use a slow shutter speed