Av (as it’s printed on Canon cameras) or A (as it’s marked on most other models) is shorthand for aperture priority mode. Why would you want to put your camera in this mode? Let me explain.
What is the aperture?
The aperture controls the amount of light that passes through a lens. A wide aperture (such as f/2.8) allows lots of light through the lens. A narrow aperture (such as f/16) only lets a limited amount of light through, as you can see from the image below.
What does Av mode do?
Putting your camera in Av mode tells the camera that you want to set the aperture and leave it to take care of other settings, such as shutter speed and ISO (which is effectively the sensor’s sensitivity to light).
Why would you want to control the aperture? Because it gives you much greater creative control over your photography.
The wider the aperture you use, the shorter the focus range (or ‘depth of field’). So if you’re taking a portrait of somebody and want to blur out the background so that only their face remains in focus, you would shoot at, say, f/2.8 or whatever the lowest f/ number your lens offers. As you can see from the photo below, shot at f/2.8, the two women are in sharp focus, while the potentially distracting folk in the background are blurred out.
If you’re taking a photo of someone and want to keep the detail in the background sharp as well, you’d shoot at f/11 or one of the highest numbers offered by your lens. This photo was shot at f/9 to keep the nice background of the golf course in focus.
How do I alter the aperture number?
There’s usually a dial on the right-hand side of a camera, near the shutter button, that allows you to alter the aperture (or f-stop as it’s called in the business). If you’re looking through your viewfinder, you’ll normally see the number printed at the foot of the screen and/or on the rear LCD display. If you’ve got a slightly flashier camera, such as the Canon 70D here, you might also see the number on a separate LCD display.
An easy way to remember how the aperture setting works: the lower the f/ number, the narrower the focus.
If you want to find out more about how to get to grips with your camera’s controls, book a place on one of my Brighton-based photography courses for beginners.