Shooting in Aperture Priority Mode
Posted on May 14, 2008 by Bo
Aperture Priority mode (Av or A) is a semi-automatic mode where you determine the size of the aperture and your camera handles the rest.
Just to give you an idea of what aperture is, it’s the opening in your camera’s lens that determines how much light passes through to the sensor (film). Think of the pupil and iris of your eye. In bright settings, the iris contracts and the size of your pupil shrinks to help cut down the amount of light that passes through. The aperture of your lens acts in much the same way. What we’re about to learn is how to control the size of aperture and use it creatively in our photography.
Aperture is measured in f-numbers, or f-stops. These f-numbers are ratios between the focal length of your lens and the diameter of the aperture. Because these numbers are ratios, it can be difficult for beginners to grasp the idea behind the numbering system. For example, f/1.4 represents a large aperture opening while f/22 represents a small aperture opening.
The size of aperture not only regulates the amount of light passing through, but it also determines the depth-of-field of your photograph. Depth-of-field is the area around the subject that is in focus. We’ve all seen pictures of a flower that’s in focus but the green field behind it is out of focus. These pictures are said to have a narrow depth of field because the area of sharpness is very narrow.
The range and number of aperture settings available to you depends on the camera and/or lens you are using. While this can vary widely, as Bryan Peterson noted in Understanding Exposure, there are three main categories in which we can group these settings: storytelling apertures, isolation apertures, and who cares apertures.
– Aperture Range: f/18, f/22, f/32
These apertures get their name from the broad depth of field that they provide. You will commonly see these apertures used in landscape and nature shots, or other shots that require most everything to be sharply in focus.
– Aperture Range: f/1.4, f/3.2, f/5.6
This is the range you’ll want to be in when you only want your subject to be in focus, but everything else out of focus. Composing shots this way will seem to isolate the subject. The lower the number, the bigger the aperture, which will then make your depth of field more narrow.
Who Cares Apertures
– Aperture Range: f/8, f/9, f/11
This range of aperture is great when your subject and background are roughly the same distance from the camera and depth of field isn’t important. If you’re shooting a close-up of someone standing against a plain white wall, who cares what aperture you use.
This range is also popular in portrait photography. Because of the broad depth of field you’ll have an easier time making sure your subject is entirely in focus.
You Try It
Now that you’ve studied a little bit about apertures, it’s time to get out there and try it for yourself. That is the best way to learn, after all.
Here’s what to do. Take your camera outside during the day, find a flower (or other singular object), and setup your camera about 3 feet from it. Get down low so that you’re not shooting directly down onto the flower/object. You’re going to need a vast background in order to see the affects of the aperture.
Now set your camera to aperture priority mode and select an aperture of f/5.6. Focus on your flower (or object) and take a picture. Trying not to move your camera, change the aperture to f/11, refocus, and take another picture. Finally, keep your camera stationary again, change the aperture to f/22, refocus, and snap one last picture.
Pay attention to the automatic adjustments your camera makes. You should see the shutter speed decreasing with each change in aperture. Because you’re stopping down the aperture each time (making it smaller), the camera adjusts the shutter to stay open longer to let in enough light to properly expose the shot.
View these images on your computer and note the differences. You now have visual examples of each aperture range we covered above. Feel free to upload your shots to the Geek Inspired Flickr group.