ODL101: Exposure

In the very first installment of ODL101, we will introduce one of the most basic (and the most important) technical aspects of photography: exposure.

Any time you take a picture, you are dealing with exposure. Without exposure, you can’t take a picture! Understanding the basics of how your camera works (even your phone camera!) will help you on your quest to becoming a better photographer.

While we will be discussing some technical photography terms, my aim is to keep this simple.

But what is our camera actually doing when we take a picture?

When we take a photo, our camera takes all available light sources and records that information on a light-sensitive medium. In digital photography, this is a sensor. (In film photography, you “expose” film.)

Your camera’s lens takes light from whatever you are pointing at, and projects (focuses) that light on your sensor. Your sensor is made up of millions of “pixels” which, for the purposes of this lesson, you can think of as teeny-tiny-light-catching “buckets.”

When your camera takes a picture, it is taking the time to “fill” all of these buckets. The more light there is, the quicker your buckets will fill. All of the millions of buckets will get different amounts of light, and will be filled with different colors. The act of filling these buckets gives you your photograph.

Desk Lamp at USS Midway, San Diego, CA. July 2014. (Canon 60D, EF 28-135mm f/3.5-5.6 IS USM)

If you look at the lamp, pictured above, you can see examples of our pixel-friends in action. The majority of the picture is black, which denotes an absence of light. These are empty buckets! There was no information for the camera to record, so darkness is the result. Right in the center of the photo, the bulb’s filament is a bright yellow, to the point where we start to lose detail. These buckets are full of light!

The rest of the lamp, where illuminated, are buckets that are partially full. The majority of pictures you take, will be focused on these half-full buckets.

So how does this help you if you’re taking pictures with your phone?

Our eyes, are really, really good at seeing the difference between light and dark in the world. Your camera’s sensor is not.

When you point your camera at things that are bright, it will struggle to capture enough light from dark areas in your shot. When you point your camera at things that are dark, it will be overwhelmed by the amount of light coming from things that are light.

Let’s take a look at a couple examples:


Oakland Zoo. November 2008. (Canon Rebel XTi, EF 28-135mm f/3.5-5.6 IS USM)

Notice how in this photo, the sky is completely devoid of any kind of detail. The camera is exposing our monkey friend correctly and, as a result, the bright light from the sky is too much for the camera to handle. The loss of detail is a direct result of “overexposure.”

Oakland Zoo. November 2008. (Canon Rebel XTi, EF 28-135mm f/3.5-5.6 IS USM)


Just moments before, we see our friend making his move up to her perch. In this shot, we can see the detail in the sky that was lost in the previous shot, however, we are now losing some details on the underside of the platforms, as well as on the subject herself. Here, the loss of detail is a direct result of “underexposure.”


With time and practice you’ll be able to use light, shadow, and the basic principles of exposure to create interesting contrasts in your images.

Glen Campground at Point Reyes National Seashore. August 2016. (Canon 60D, EF-S 10-18mm f/4.5-5.6 IS STM)

The important thing is to be aware that your camera does have limitations, and to use them to your advantage!

Respect your buckets!

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