A camera is nothing but a box with a hole in it. The hole opens and closes, allowing light to enter the box, and this light is recorded onto film.

You can control how much light, called the “exposure,” your camera uses through three basic functions: aperture, shutter speed, and ISO. The aperture is how big the hole in your camera is; the shutter speed is how long you leave the hole open; and the ISO is your camera’s sensitivity to light.

The right balance of these three functions will produce the perfect exposure and a good-looking photo; but getting your head around these functions is not a snap. To understand how they work, it’s easier to think about light through “the window analogy.”

Pretend you’re in your living room, looking out your window. Now imagine that your window is the aperture, which determines how much light enters your camera. Depending on the size of your window, the amount of light will change. A big window will let in more light, whereas a small window will let in less.

Your window also has some shutters on the outside. The shutter, of course, is the shutter speed of your camera. It represents the amount of time your camera’s shutter stays open and lets light into your living room.  If you close your shutters quickly, less light will shine through the window, so your room will be less well-lit (your photo will be darker). But if you close them slowly, then more light will be able to come through over time, which will make your room more well-lit (and your photo lighter).

In case the light gets too bright, you also have your sunglasses with you. Your glasses are the ISO, which determines the camera sensor’s sensitivity to light. If the room is too bright, you would wear your sunglasses and your eyes would desensitize to the light.

Together, the size of your window, the amount of time you keep your shutters open, and whether you wear sunglasses or not will all determine the exposure of your photo.

Let’s say that you’re taking a photograph on Mount Royal at night and you really want to lighten up the Montreal skyline. To do that you would need to make a bright exposure—you could widen your aperture, increase your ISO number, or choose a slower shutter speed.

Be careful not to overexpose your photo too much; you want to find the exposure that’s just right. In a situation where the light may already be too bright, you would want to use a narrow aperture, a low ISO number, and a high shutter speed.

Experimenting and playing around with these three functions will help you get the exposure you want to produce a great photograph!

Aperture range

f/1.4 is considered a wide aperture, and as the numerical value of the aperture increases, the actual size of the aperture decreases. An f/8, for example, is a narrower aperture than an f/5.6.

ISO range

An ISO number can range anywhere from 100-56,000. A high ISO like 1,600 makes your camera very sensitive to the light whereas the lower the ISO number, the less sensitive your camera is to light.

Shutter speed

The typical range of your shutter speed ranges from the fastest being 1/1,000 of a second to the slowest being 1 second.