Now that we have touched on ISO, lets take a look at shutter speed on your dslr. Shutter speed controls how long the shutter is open which allows light to hit your camera’s sensor. In an image where it is bright and sunny, you want the shutter speed to be quick so it doesn’t overexpose the shot, like 1/250 sec. But if you have a dark situation, shutter speed can help get the perfect exposure by you selecting a slower shutter speed. This way the sensor has ample time to collect the light and detail of the shot before it closes, but beware, slower speeds can show camera shake so be sure to use a tripod if choosing a slow shutter speed.
Camera shake occurs when you or your subject moves while the shot is being taken. If you want to freeze the action or make sure there is no camera shake, the shutter speed needs to be at least 1.6x the amount of your focal length you are working with if you are using a camera with less than a full size sensor. For example, if you are shooting at a focal length for portraits, say 50mm, then your shutter speed needs to be at least 1/80th sec. to avoid camera shake. I usually set my shutter speed to 2x my focal length or more to freeze the action and make my shots tack sharp.
Another way you can use shutter speed creatively is to slow down your shutter speed. Photographers who want that milky look to water falls have to slow their shutter speed to 1/5 sec., for example, to let the water become blurry. If you are in a sunny area or it is too bright to slow your shutter speed and not blow out your image, you can close down your aperture (more on this later) or attach a neutral density filter to your lens which will cut the amount of light reaching your sensor. ND filters come in different strengths for different needs so it is handy to have at least two in your bag. Whichever way you choose to restrict the light, you will need to use a tripod for shots like this or at least place the camera on something sturdy and shoot with a wireless trigger.
Panning is another way to be creative with your images. To capture the sense of speed, you can set your camera on a slower shutter speed, and while your subject is moving past you, try to follow it while you are taking your shot. If you can get the hang of it, the image will come out clear on your subject but everything else will be blurred.
Now that we have taken a look at another part of the exposure triangle, keep in mind that when you make a change to one thing, you need to make an opposite change to something else to maintain a perfect exposure. We will now take a look at the final piece of the exposure triangle in our next post in this series: Aperture.