Department of Creative Arts
St. Pius X High School

Ms. D. Gravelle

I3 - Exposure




The most important aspect of every photograph is light. Without light there is no photograph, and as such we need to learn how to use the available light to our advantage. The first thing we need to learn is how to take a correctly exposed photograph.

Exposure is simply a term used to describe the brightness of a photograph. When you press the shutter button on your camera the camera’s sensor is exposed to light, subsequently recording the image and displaying it on your screen. Sometimes things can go wrong though.

Have you ever taken a photo and it’s turned out completely white or black? I definitely did, and that’s simply a case of something going wrong during the exposure. There are only three things that can go wrong here: Shutter speed, aperture, and ISO. This is referred to as the Exposure Triangle.

The Exposure Triangle
Shutter Speed – Every camera has a shutter. It’s the mechanism that blocks the digital sensor from light until the moment we decide to press the shutter. The speed with which it opens and closes unsurprisingly effects the amount of light that passes through, therefore affecting the brightness of your photograph. Too fast and not enough light passes and makes your image dark, whereas too slow and too much light hits the sensor and renders some or all of your image completely white.

Aperture – All camera lenses have an aperture inside them, which is a small opening that directs light towards the sensor. On most cameras the aperture can be made wider or narrower, therefore altering the amount of light passing through and effecting the final image’s brightness.

ISO – The term ISO has it’s origins back in the days of film photography, when it was used to describe a certain film’s sensitivity to light. Now, it’s used in similar circumstances on digital sensors, whereby adjusting the ISO changes how sensitive your sensor is to the light hitting it. A higher ISO means more sensitivity, resulting in a brighter image. However, the higher ISO you use the more digital noise you introduce to the image.

How Does All This Tie Together?
This is something a lot of newcomers to photography struggle with, and it results in a lot of frustrated amateur photographers wondering why their images keep coming out too dark and how they can fix it. I usually find that it’s because they were taught in over complicated terms, when in actual fact it’s very simple:

If one of your three variables (shutter speed, aperture, or ISO) changes, then in order to keep the same brightness another must change an equal amount in the opposite direction.

Changing just one of your variables alters the brightness of the final image, so if you find that your image is too dark just try changing one of these three things until it’s correctly exposed.

The story doesn’t end there though. Altering the shutter speed, aperture, and ISO does have other effects besides changing the brightness. Don’t worry about that though, we’ve got that covered in the article below:

I3.T1 - Canon Learn

Work through the Canon Learn website to better understand apeture, shutter speed, ISO, and exposure

I3.A1 - Canon Play

Using Canon Play take at least 10 photos that illustrate different Exposure, Depth of Field, and Motion. Take a screenshot of each image with the settings visible. Post all of your images on your website, clearly indicate what shot you would keep as your final image.

I3.A2 - Canon Challenge

Complete the Canon Challenge to reproduce 6 images. Keep trying until you get a perfect score. Post a screenshot of your score and time.