Now that you have reviewed and understand aperture, it is time to dive into shutter speed. If you missed the aperture post, take a look. It's important to understand because aperture and shutter speed go hand in hand. The shutter on your camera controls the amount of time that light hits your sensor, thus creating an exposure. It's kind of like a curtain. The slower your curtain opens and closes, the more light is let in. The quicker the shutter opens and closes, the less light enters. Your shutter speed not only effects your exposure (making it brighter or darker), it can show movement or freeze motion in a photograph. Shutter speed is measured in fractions of a second (i.e. 1/2 1/4 1/8 1/15 1/30 1/60 1/125 1/250).
Here's a little visual aid to help you understand shutter speed:
In the image below, we can see that the subjects are blurry. This happens when the shutter speed is slow, using a larger fraction. In this photo, I used 1/20 which made the people blur from movement.
When using a tripod, slow shutter speeds (also called long exposures) can make for great landscapes. In this image, I used a tripod and shot before sunrise using a 30 second shutter speed. This showed the movement of the stars and let in more light from the sun rising, well before the sky was even light. We'll cover more about long exposures another time.
The image below is crisp and sharp, even though it is of a moving subject (riding quite fast in a triathlon, nonetheless). You can freeze or capture motion if you use a fast enough shutter speed, or a smaller fraction such as 1/800. I used 1/250 for this image, with a 50mm lens.
When dealing with shutter speed, we also need to consider camera shake (blur from your hand holding your camera). A good rule of thumb when trying to avoid camera shake is to use a shutter speed that corresponds with the focal length of your lens. If you have a 200mm lens, you'll want to try and use a shutter speed of 1/250 or higher, to avoid camera shake. If you have a 50mm lens, try to shoot above 1/60. Using a tripod definitely helps to avoid camera shake, but these little tips will help you when a tripod isn't handy, because let's be honest, who wants to haul around a tripod everywhere?
For a little review, think of this: aperture is the AMOUNT OF LIGHT that is let in your camera. Shutter speed is the AMOUNT OF TIME that the light is being let in! These settings are key to shooting on manual, which is absolutely, totally and completely awesome. You can do it.