The third point on the Exposure Triangle is shutter speed. The camera’s shutter speed is usually measured in fractions of seconds– and tiny fractions, at that. Like aperture, shutter speed determines how much light can go to the sensor at a given point in time. Aperture does this by getting wider or narrower (like the pupils in your eyes). Shutter speed does this by opening and closing for a period of time.
Think about the shutter like a door. Let’s say you hear something outside. It’s a bright day with plenty of light, so when you open the door it doesn’t take long to see that the noise was a kid on their bicycle.
Now, let’s say it’s at night and you hear something outside. You open your door, but it takes longer for your eyes to adjust so you can see the Trick-or-Treaters coming up the front step.
Now, the shutter speed you’ll need to use depends upon your subject. Photographing sports? You’ll want a fast shutter speed, something like 1/500-1/2000 depending on the available lighting. For everyday candids of friends and family, shutter speeds of 1/100-1/500 will be just fine. If your shutter speed is slower than, say, 1/60th of a second, you’ll want to put the camera on a tripod. Why? Because if the camera moves while the shutter is open, then that motion will show up in the picture as blur.
If you have an ‘S’ or ‘Tv’ mode on your camera, that is the Shutter Priority mode. It allows you to set the shutter speed while the camera will set the aperture and ISO for you. Try adjusting the camera to various shutter speeds and see what happens.
Here are some examples of photographs taken at various shutter speeds:
1/500th of a second:
For fast action and sports, a faster shutter speed freezes action. When you’re photographing indoor sports, be aware that the faster the shutter speed is, the less light is hitting the sensor. If you push the shutter speed too fast, the pictures could end up dark.
1/250th of a second:
In this photo, the firedancer wasn’t moving very fast, so a shutter speed of 1/250th of a second was enough to freeze her motion, though the flames are blurred because they were moving fast enough that their motion shows up.
1/125th of a second:
The dog was laying on the floor, looking sad because we wouldn’t give him any chocolate chip cookies. Because he was sitting still, a 1/125th of a second was fast enough for this shot. 1/125th is usually fast enough for general candid shots of people.
In this photograph, 3 seconds is long enough for the motion of the fountain to make the water look silky, and it shows the the walking tourists and the traffic in the background. The people sitting on the fountain’s edge were sitting still enough for those three seconds to not be blurred out.
I had to use a 10-stop neutral density filter for this photograph. It’s a nearly opaque filter that allows a photographer to use very long shutter speeds in the middle of the day. That’s why the water looks silky, and why the clouds look so wispy. The exposure was long enough to show the motion of the water, the mist of the falls, and the clouds moving through the sky. If you look really closely, those little shapes at the base of the waterfall are people walking around. That long shutter speed shows their motion.
Together, aperture, shutter speed, and ISO work together to give you a proper exposure. They work independantly of each other, but they also affect each other. If you change the aperture, it will change which shutter speed you’ll need. If you change the ISO, it will change which aperture you’ll need. And so on and so forth. There is no one way to set the camera. If all depends on the situation and how you want it to look.
And as always, the best way to figure out how all of these settings affect each other is to practice.