Today's Photo Skill: Controllers of the Light

Last post I recommended that, if you're new to photography, you find the light and use it. Banish the dark mystery photos. Today I want to move into Exposure. You can have the best subject and an eye-catching composition, and if the exposure is all wrong, no one will ever know.

Exposure is how much or little light we let onto the camera's sensor. An overexposed picture is way too bright, and an under exposed picture is way too dark. Just browse Facebook and you'll find abundant examples of both.

While the study of exposure is a huge subject, and there's no way we're covering it all here, I plan to spend the next couple of posts on exposure and how the light is controlled for that perfect shot. For our purposes lets leave artistic exposure out of the equation for now. Let's explore perfect exposure, which is a balance of the brightest areas of the image not being blown out (so bright that there's no data there) and the darkest areas still having some detail.

There are 4 main controllers of exposure. They are the Aperture, the Shutter, ISO and Exposure Compensation. For this week we are going to focus (pun intended) on what role each plays in good exposure.

Aperture is the opening that lets the light into the camera. So controlling the size of the opening controls how much light gets in. Aperture is measured in f-stops. The range of f-stops on different cameras and if you have a camera system with interchangeable lenses, it's the lens that controls the range of f stops. The numbers like 2.8, 3.2, 4.0, 5, 5.6, 6.3... 18, 22 indicate the size of the opening with (in this example) f2.8 being the biggest opening and f22 being the smallest. There are other aperture considerations than just the light being allowed in, however for today's discussion, we need to understand small and big and that the numbers are the inverse.

Shutter is the device that opens and closes to let in the light. The speed of the shutter determines how much light gets in. Shutters can be very slow - a second or more, moderate - 1/40th or a second to 1/250th of a second, to very fast to stop movement - 1/500th to 1/2000th of a second. The slower the shutter speed the more light and vice versa.

ISO (aka ASA for those who like alphabet soup) refers to the sensitivity of the sensor. The more sensitive we make the sensor the more light can be seen and consequently the grainier the images. A low sensitivity like 80 or 100 or 200 will produce the clearest, sharpest images (low grain) and a high sensitivity like 800 or 1600 or 3200 will be somewhat grainy (dependent on the camera) but tolerate lower light conditions and still get a good exposure. 

Exposure Compensation is used when you are taking advantage of your camera's automated modes, where the camera is determining exposure for you with some or even no input from the photographer. Sometimes you want a little more or less light than the automatic setting provides and the exposure compensation setting is how you add or subtract light.

Putting all of these together to get a perfect exposure is a portion of the art of photography. It's a delicate balancing act. So for the next few weeks we'll explore first each of these controllers in more detail and then we'll explore the interplay between them.

For this week, think about the 4 controllers and how you might use them with each image that you make. 

Shoot lots & dream big!

This is a little video which is from a private training where we focused on these aspects of exposure. Watching it will reinforce the information above.