Camera Settings: Aperture Priority

Exactly one year ago, I eagerly took my fancy new camera out of its box and set it in my lap just so I could stare at it. I never thought I would own such a magnificent piece of equipment! I gazed down at it with excitement, and then I scratched my head and said, "Oh dear. How do I work this thing?"

At first I started rotating dials and pushing buttons and scrolling through menus. Then I realized that I truly wanted to know what I was doing, so I did massive amounts of research. Books, the internet and a couple smart friends taught me loads of valuable information about my sparkly toy. I have so much more to learn about my camera. I never want to come across as being a know-it-all because I'm most definitely not. I only talk or write about topics that I have a good understanding of.

The most important thing (for me) to learn about first were the different modes my camera could shoot in. Since I shoot in aperture priority mode a lot of the time, I will explain this mode first.

First of all, what is aperture? Aperture is what controls the amount of light that reaches the camera's sensor. The explanation that helps me to understand it the best is that the aperture is like the pupil of an eye. It opens wider in low light so it can let in whatever light is available. It gets smaller in bright light so it can reduce the amount of light entering in.

When I shoot in aperture priority mode (Av on the mode dial for my Canon 40D), I am telling my camera's aperture how wide or small to set itself. These settings are called f-stops. The higher the f-stop number, the less light is allowed into the camera. And the lower the f-stop number, the more light is allowed into the camera. An f-stop of 1.8 (usually expressed f/1.8) will let in more light than an f-stop of 6.

Shooting with a wide aperture (a low f-stop number) allows me to take a photo with a shallow depth of field. My main focal point remains in focus while everything in the foreground and/or background becomes blurred. I personally love this effect when I am shooting portraits, or any object close up.

Bif's right eye is totally in focus in this photo. Even as close up as his left eye and his ear are starting to blur. This shows the very shallow depth of field, which is a result of the 1.8 f-stop.

Again in this one, there is an f-stop of 1.8. Sammy's eyes (and left hand) are in focus, but the foreground and the background are blurry. This is another example of a shallow depth of field. Anything that is on even a slightly different plane than the focal point (Sam's eyes) starts to blur.

Shooting with a small aperture (a high f-stop number) creates a deeper depth of field. This results in photos that have more planes in focus. This is good when shooting landscapes or scenes where there isn't just one plane to focus on.

The flamingos are all on different planes (depths), yet they are all in focus. My camera had an f-stop of 5 when this photo was shot, so the focus extends more deeply into the photo than the above examples.

And here I shot with an aperture of f/13. I wanted the entire scene to be sharply in focus.

When shooting in aperture priority mode, the aperture setting is the value I have to set on my camera before I take the photo. Once the desired aperture is set, the camera adjusts the shutter speed accordingly, and it tells me if the number I set for aperture is not appropriate for the amount of light present. It doesn't actually tell me. That would be freaky. But the number blinks. When this happens, I know to adjust the aperture until the number on the display stops blinking. Or, sometimes I ignore the blinking number and take the photo anyway just to see what happens.

That, my friends, is a very long-winded explanation of aperture priority.