How to Use Aperture Priority in DSLR Camera
For photographers who use SLR cameras, AV or A (AV for Canon or A for Nikon) mode determines whether all the photograph is in focus or part of. For example photographers can choose to have a sharp foreground and background, or they can blur the background.
Aperture is indicated by a f-number value.
For instance if you're taking a photograph of a landscape, chances
are you will want all of the foreground and background to be sharp
and in focus. For this to happen you will need to set your digital
camera f value or aperture as its known, to a large number,
for example F/11.
On the other hand if you're taking a photograph of a bird and you
want the animal in focus but not the background, then you would
choose a small F number like F/4.
You can see what aperture your digital SLR camera is set at
by looking at the back LCD screen for a F number. As you can
see by the image above right, the aperture in that example is set at
F4.0. The display shown on your LCD may look different to this
example, depending on the make and model of your camera.
How to set your camera to aperture priority?
Your camera then changes all other settings such as shutter speed automatically to suit.
Once you have AV mode turned on, you can change the f-number by
rotating the main dial above the shutter button. Note: this is for Canon
digital cameras. You may need to refer to your manual to find out how
to change the F stop for your specific brand of camera.
When the f number is small, the lens
diaphragm is actually wide open.
So if someone says to you that you need
to open your lens more,
they mean to lower the aperture or F
number. Alternatively, if the
aperture is a large number, say F22 then
the lens diaphragm is smaller
or more closed. This often causes much
confusion with beginners.
- Opening your lens more refers to lowering the f number.
- Closing your lens more refers to a higher f number.
Take images at both ends of the scale. One with as low a F number as possible and one with as high a F number as possible. More importantly, when you view them on your computer take notice of how much of the photo is in focus.
Photography Assignment - Grab your DSLR camera and give this a try
Understanding how each mode works separately, is vitally important before trying M (manual mode). Learn how to use aperture priority and how different F numbers effect the overall image. Then and only then, will you fully understand how to use it when shooting in manual (M) mode.
Assignment: Lesson in aperture priority mode
- Set your digital SLR camera to aperture priority mode. For Canon users, this means turning your mode dial to AV. Nikon users need to change the dial to the letter A. If you don't see the letters AV or A, then refer to your camera manual.
- Change your camera's aperture F
stop to the lowest number possible for your lens. It's important to
note that each lens will be able to shoot at different apertures.
Expensive lenses can go as low as F1, where most on average will be able to shoot at around F4.
- Go outside and photograph a close object where
the background elements are far away in distance. This is extreme to
ensure you easily see the visual differences as you change the F number. On a low F number, you should notice the background is very blurred, when compared to the main object that is in focus.
- Now change the aperture number to around F7.1 and take the shot again.
- Take two more photographs, firstly with an aperture of F11, and then F22.
- Download and open all 4 photographs on your computer and see the difference that can be seen in the background. Notice the lower the F number, the more blurred the background. The higher the F number, the more of the background that is seen in focus.
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