The Exposure Triangle: Aperture

It is essential to understand the exposure triangle in order to capture high quality footage that is perfectly exposed for your project. What is the exposure triangle? Proper exposure is important for both still and video photos. Aperture, Shutter Speed and ISO. In future articles, I will cover Shutter Speed as well as ISO. Here, we’ll be focusing on aperture.
What exactly is aperture?
Aperture can be viewed as the pupil of the lens. It allows more light to the sensor when it is open (lower f/stop#). It allows LESS light to the sensor if it is more closed (higher f/stop#).
A camera aperture has a few more features. It controls the amount of light hitting it, as well as Depth of Field. This is how blurred the background is in your photo or video. This is important because when you open the aperture to let more light in, it also SHOWS your Depth of Field. This can make it a little harder to keep your focus on your subject, especially if they are moving.
Here’s an example of a Buck Showalter bobblehead. (Go O’s! ).
The first image (top right) shows how the subject is sharply focused and the background blurry. This is sometimes called bokeh. In the final image, the subject remains in sharp focus, but the background is almost in focus. The exposure of the images has not changed. This is because I used a much LONGER shutter speed to capture the image, as I closed the aperture to f/22.
The aperture controls how much light is allowed onto the sensor. If I want to alter the amount of light hitting the sensor and maintain the same exposure, then I need to modify something else in the triangle. In this instance, I had to adjust the shutter OPEN for longer periods of time in order to maintain the same exposure because I was closing down the aperture (allowing less light onto the sensor). I could have kept the shutter speed unchanged and adjusted the ISO sensitive, but that comes with its own set of considerations. This is where the triangle comes into play. We’ll be covering the other corners of the triangle in future posts.
Hopefully, you now realize that aperture is more than an exposure setting. You can open the aperture to make your photo appear brighter, or you can close it to make it darker. But there’s more to it. Rarely do I think of changing the aperture to alter exposure. The powerful tool of aperture can make your photos more visually appealing. Aperture can only be used creatively if you understand how it affects your exposure.
Here’s another example.
A couple of years ago, I had the chance to shoot a music clip for Nelly’s Echo, a good friend and local musician. You may also recognize him from The Voice.
It was a beautiful day in Baltimore. It was difficult to balance all the bright sunlight bouncing off of the buildings while still keeping the background creamy and blurred in most shots. Nelson, the lead singer of the band and the namesake, was walking down the street while he sings. We alternated between a wider shot that showed Nelson from the waist up and gives you a sense for the place by showing the movement of the city and a closer shot to capture the emotion in his face.
The wider shot was to show the city but not distract from Nelson. The background should be blurred, but not completely out of focus. I wanted the focus to be solely on Nelson for the tighter shot. This is where I was able use my knowledge of aperture to my advantage.
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