The Light Chaser: Aperture.

An image created using a wide-aperature, which reduces the focus of the background.

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The Light Chaser. A blog by Rob Alway. 

Chapter 5: Exposure — Aperture.

Over the past two weeks we have been discussing exposure. In Chapter 3, we discussed ISO. In Chapter 4, we talked about shutter speed. Today, we address aperture. While shutter effects motion and light, aperture effects focus and light (do you see the common theme here? Everything you do on a camera effects light).

Aperture is controlled through a diaphragm located on the lens. It basically is the same concept as the iris in your eye. Typically, when you are in bright light, the iris in your eye gets really small. It tends to open wide in darker conditions. This is the foundation of aperture.

Aperture is measured in f-stops. While f-stops have a mathematical logic and pattern to them, that information isn’t as important as knowing what the f-stops do. Here are the basic f-stops that most professionals learn in a beginning photography class:

f/1.4, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22.

If you adjust aperture on your digital camera, at the minimum you will notice some or all of these f-stops, depending on the size and quality of the lens. Many lenses also allow for 1/2 or 1/3 measurements as well.

Beginning from the smallest number, each f-stop allows in twice the amount of light as the previous. This also impacts the depth of field (or depth of focus) of the image. A small opening, such as as f/16 or f/22, is going to mean the image will be in focus from foreground to background. A wide opening, an f-stop such as f/1.4 or f/2.8, is going to give allow you to focus on a specific portion of the image while the rest of the image (or the different planes) will be out of focus.

Using a narrow aperture keeps the image sharp from foreground to background.

The second thing that aperture impacts is light. A wide opening is going to allow you to photograph in darker conditions using a faster shutter speed. This is why you see sports photographers carrying large, wide lenses. These lenses allow for f-stops such as f/2.8 and at the same time allow for faster shutter speeds to freeze motion.

Next week we are going to take a break from exposure and talk about one of my favorite places to photograph. Then, we will talk about the joys of measuring light!

Rob Alway is editor-in-chief of Media Group 31, LLC, owner of Mason County Press, Manistee County Press and Oceana County Press. He is also a professional photographer with over 25 years of career experience and an adjunct instructor of photography at West Shore Community College. He and his wife, Becky, own Alway Photography, Inc. of Scottville.