Photographers, do you know what your medium is? For other forms of art, the answer to this question is easy: painters use paint, sketchers use pencil, and musicians use sound. But as a photographer, your medium is light.

Many beginner photographers have trouble grasping this concept. Perhaps it's because light is such a difficult thing to understand. In fact, scientists have only recently made major discoveries about light that shape our beliefs and use of it.

Here are some things you should know about light:

First of all, light is "stuff." It will really help you to understand how to work with it if you know that light is actually made up of tiny particles that spew from light sources, like light bulbs, flashes, and the sun. I like to think of light being like water. Spotlights spray light in a very concentrated way, like a garden hose. Umbrellas and softboxes spray light in a diffused way, like a soft misting spray bottle. The sun sprays massive quantities of light particles in every direction. Every light source emits light differently.

Your camera lens captures the light particles and focuses them onto a film or digital sensor. This will either make a chemical transformation on the film, or an electrical transformation on the digital sensor. This is what creates your image.

Light particles move fast. Really fast. In fact, light moves so fast that it took scientists thousands of years to even know that it moved at all. Light particles travel at approximately 186,000 miles per second, or 300,000 kilometres per second.

Light bounces. By using white or silver reflectors made of cardboard or styrofoam, you can bounce light from its source onto the shadow areas of your subject. Some light is always absorbed when it is reflected like this, so you don’t have to worry about the reflected light overpowering your main light source. Experiment with reflectors. They can result in more even, better-lit photos.

Light doesn’t bounce off everything equally well. Just as the hardness of an object affects how a tennis ball bounces off something, the color of an object affects how light bounces off it. Darker colors actually absorb more light, so less of it will reach your camera. Bright colors reflect more light, allowing more of it to reach your camera.

Your camera knows less about light than you do. In automatic modes, cameras assume that the light they are measuring is bouncing off of a surface that is a medium grey color (18% grey). You need to compensate for this. If you are photographing a subject brighter than 18% grey, like a snow-covered field, or a beach, you should switch to manual mode and decrease your shutter speed (make a longer exposure) or use a larger aperture. Conversely, if you are photographing a dark-colored subject, increase your shutter speed (make a shorter exposure) or use a smaller aperture. These techniques will ensure that the right amount of light gets into your camera, and creates a proper exposure that more accurately reflects the scene.

Allowing too much light to hit your film or sensor creates an overexposed image. Too little light creates an underexposed image. Your camera’s controls give you the ability to manipulate the quantity of light particles entering your camera. Shutter speed determines the amount of time for which light is allowed to enter the camera. Aperture determines the rate at which light enters the camera. By adjusting the shutter speed and aperture of your camera, you can precisely control the duration and flow of light into your camera. Think of light particles as people waiting outside a building (your camera). The door (shutter) is closed. Opening the door wide (wide aperture) lets a lot of people in. Opening it only a little bit (small aperture) lets people in more slowly. Leaving it open wide for one minute (shutter speed) will let the same amount of people in as leaving it half open for two minutes. You want to control the number of people entering the building. Too many people, and the building will be overcrowded (overexposed). Too few people, and the building will be empty and lifeless (underexposed). How long do you have to open the door, and how wide, to get exactly the right number of people in?

Light doesn’t always have to come from in front of your subject. Try placing the light source behind your subject, or off to the side. Observe how the light bounces off your subject and creates interesting shadows. Play with the light and catch it in your camera. You’ll be happy with the results.