Every photographer should know how to manipulate the exposure triangle to achieve the photograph they desire. Don’t worry: the exposure triangle is not geometry-related. It’s just a term people use to describe the three elements of photography that determine exposure. Mastering these techniques will not only improve your exposure, but also your composition and overall quality of work.

Aperture

If you look at your lens, you’ll see that there is a hole in it. This hole allows light to enter the camera and create your photograph, and it’s called the aperture. The size of the aperture varies by lens; some zoom lenses have a variable aperture, meaning that as the lens zooms in or out, the aperture changes. On the other hand, a fixed aperture does not change as you zoom in or out. Aperture sizes are notated with an f, which represents a complicated ratio that you don’t really need to know. The most common ones are f/1.4, f/2.0, f/2.8, f/4, f/5.6, f/8, f/11, f/16, and f/22. Even though it may seem backwards, the larger the aperture number, the smaller the opening.

Aperture is also a component in determining the depth of field, which is basically how much information is in focus in the photograph. The smaller the aperture is, the shallower the depth of field is; the larger the aperture is, the deeper the depth of field is. What does this mean exactly? A shallow depth of field has a small area in focus, whereas a deep depth of field has a large area in focus. Check out the example photographs below to get a better understanding.

Shutter Speed

Image a door inside your camera that opens to let the light in; that is what the shutter does. It opens and closes to expose the digital sensor to the light coming in through the lens (controlled by aperture). The shutter speed is how fast the “door” opens and closes. It’s measured in fractions of a second. The most common speeds are 1/1000, 1/500, 1/250, 1/125, 1/100, 1/60, 1/30, and 1/15. Obviously, the smaller the fraction, the faster the shutter moves. The best speed to hand-hold a camera is at or greater than 1/60.

The shutter speed determines how quick action is caught. The faster the shutter speed, the quicker action can be stopped. For example, shooting someone walking at 1/60 will probably turn out good, but photographing a jogger at 1/60 will probably turn out blurry. The faster the action, the higher the shutter speed will need to be to capture it.

ISO

This last element determines how sensitive the sensor is to the light it’s absorbing when the shutter opens. The most common ISO settings are 100, 200, 400, 800, 1600. Some cameras have ISO that go higher than 10,000. The Nikon D4S can reach 19,034 ISO.

The negative side to ISO is that the higher the number, the more grain in the image. The only time you should seriously consider touching your ISO is if you are in a low-light situation. If you are in a dark location, you should first shoot with a lower shutter speed and use a tripod to stabilize your camera, without touching your ISO. Some artists like the grain look and shoot with a high ISO on purpose, but most prefer the smooth and crisp look of a low ISO.

Exposure

What is exposure? Basically, it is the amount of light in a photograph. You can have a perfectly exposed photo, or one that is under or over exposed. Underexposed means the photo is too dark, and over exposed is too bright. The balance of these three elements determine the perfect exposure of a photograph. Each lighting scenario will have a different balance, and as the lighting changes you’ll have to readjust your camera accordingly. If the balance is not right, your image will either come out under or over exposed.

A small aperture, slow shutter speed, and high ISO all allow a great amount of light in. On the other hand, a large aperture, fast shutter speed, and low ISO allows less light in. The best way to balance the triangle is to have one setting that allows a lot of light in, and another that has less light. For example, if you were taking photos of someone standing still, you may opt for a large aperture and slow shutter speed. At a sports event though, you would probably want to set the camera at a fast shutter speed and small aperture.

This is a picture of a duck I took at a local marina. I wanted just the duck to be in focus, so I got as close as I could to him and lowered the aperture to achieve a narrow depth of field. I increased the shutter speed to account for the low aperture, but also because the duck was moving around a lot. Because it was a sunny day, there was plenty of light and I was able to leave the ISO at 100.

Once you've mastered the technique of the exposure triangle, you'll begin to understand how your camera works and make better photographs. Try it out for yourself; find a subject to practice on and throw your camera into manual!