Shutter speed, along with aperture and ISO, is part of the exposure triangle. Shutter speeds are almost always written in seconds or fractions of a second.
There are a few main types of shutters, which are covered in the shutter section. They all function slightly differently but their main goal is to control the length of time light is falling on the sensor, film, or recording medium.
Just like learning to control the aperture is part of the photographic process, learning how shutter speed impacts your photos is equally important.
Shutter Speeds Help Control Motion
Shutter speeds control how much motion blur is present in a photo. Motion blur comes in two different varieties. Camera shake is accidental motion blur caused by the person holding the camera at a slow speed. Intentional blur is when you decide to use settings that either impart blur into the photo or freeze motion; it’s purposeful.
Camera shake is a fairly easy problem to solve. In order to remove camera shake, increase the shutter speed and compensate by changing your ISO or aperture. A good rule of thumb is to follow the 1/focal length rule. That means that, usually, as long as you are shooting faster than whatever your focal length is, your photo will be acceptably blur free. As an example, if I am using a 200mm lens, I would try to avoid shooting under 1/200th of a second while hand holding.
Newer lenses and bodies may have stabilization aids built into them. From what I have seen, they always measure the effectiveness of the stabilization in terms of stops. That means that you can shoot hand-held at however many stops the images stabilization is rated for. For example, a 300mm lens with two stops of stabilization should be able to be hand-held down to 1/80th of a second. (In practice, I have not found this to be true on larger lenses which are excessively heavy.)
Some manufacturers claim that using a lens with image stabilization on a body with sensor stabilization allows you to stack the stabilization. So, a Nikon lens with two stops of stabilization mounted on a camera with three stops of stabilization abilities could theoretically give you five stops of stabilization. That would mean that same 300mm lens with two stops of stabilization would be able to be hand held at 1/10th of a second! (Again, I doubt the effectiveness in longer or heavier lenses)
Another way to avoid camera shake is to use a monopod or tripod when shooting at slow speeds. Tripods are usually more stable than monopods. Quality tripods are usually rated in weight. Generally, buying a tripod that can support twice the weight of your camera will provide you with the sturdiness that you need in the max taxing situations.