how to
photograph
wild birds

Lesson 8

Let's shoot photos in Av (aperture priority AE) mode

I want to blur the background so that birds eating in the bushes stand out. This can be achieved by changing to Av mode (also known as A mode on some cameras).

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Grey Heron
Grey Heron
Grey Heron
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This photo is flawed because of the branch crossing in front of the bird's face. Nevertheless, I tried shooting this scene to show how the aperture setting can change the photo.

Image data
  • Aperture value: f/4
  • Shutter speed: 1/2500 second
  • ISO speed: ISO1600
  • Exposure compensation: -0.3
  • Focal length: 500mm
  • DSLR Camera (APS-C image format)

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What kind of photos can I take using the Av (aperture priority AE) mode?

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Av (aperture priority AE) mode lets the photographer select the aperture (f/number). With a low aperture f/number, the background becomes blurred, whereas with a high aperture f/number, the entire photo is sharp, both in the foreground and background. Therefore, adjusting the aperture changes the amount of blurriness that appears in the image.

Note: The higher the f/number, the narrower the lens's aperture diameter. The displayed f/numbers vary between lenses.

What is focus range (depth of field)?

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Changing the aperture (f/number) alters the range that appears in focus in a photo. This focus range is called the depth of field. In photos with a deep depth of field, all aspects of the image appear in focus, from the foreground to the background. Conversely, in photos with a shallow depth of field, only objects located within a narrow range of distance from the camera appear sharp while the foreground and background are unfocused.

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Comparison of the effects of different aperture (f/number) settings

Let's experiment with different aperture (f/number) settings

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1 Set your camera's shooting mode to Av (aperture priority AE).

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2 Adjust the aperture (f/number) setting. Take photos while turning the dial and noting the numbers displayed in the viewfinder.

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Turning the dial to adjust the aperture (f/number) setting

3 The lower the f/number, the wider the aperture and the shallower the depth of field. The higher the f/number, the narrower the aperture and the deeper the depth of field.

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It is easier to adjust the aperture by looking through the viewfinder as you turn the dial.

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Comparison of the effects of different aperture (f/number) settings

A standard depth of field (f/8)

The background is moderately blurred. The main subject stands out and the feel of the background is maintained.

  • Aperture value: f/8
  • Shutter speed: 1/250 second
  • ISO speed: ISO800
  • Exposure compensation: -0.3
  • Focal length: 500mm
  • DSLR Camera (APS-C image format)
Image
Grey Heron(Aperture f/number: f/8)
Grey Heron(Aperture f/number: f/8)
Grey Heron(Aperture f/number: f/8)
Enlarge

A deep depth of field (f/22)

The bamboo thicket in the background is clearly recognizable. The leaves of the bamboo in the foreground and the branch in front of the bird's face are also distinctive, distracting us from the main subject.

  • Aperture value: f/22
  • Shutter speed: 1/60 second
  • ISO speed: ISO800
  • Exposure compensation: -0.3
  • Focal length: 500mm
  • DSLR Camera (APS-C image format)
Image
Grey Heron(Aperture f/number: f/22)
Grey Heron(Aperture f/number: f/22)
Grey Heron(Aperture f/number: f/22)
Enlarge

A shallow depth of field (f/4)

The branch in front of the bird's face has been blurred, making it less distracting since it's difficult to recognize its shape. The background is so blurred that the patterns in the bamboo thicket are indistinguishable. The grey heron stands out against the green and blue gradations of the background.

  • Aperture value: f/4
  • Shutter speed: 1/1000 second
  • ISO speed: ISO800
  • Exposure compensation: -0.3
  • Focal length: 500mm
  • DSLR Camera (APS-C image format)
Image
Grey Heron(Aperture f/number: f/4)
Grey Heron(Aperture f/number: f/4)
Grey Heron(Aperture f/number: f/4)
Enlarge

Relationship between aperture, shutter speed and brightness (exposure)

In the photos above, the ISO speed was fixed at ISO800. When the aperture (f/number) is changed manually, the camera automatically adjusts the shutter speed to maintain the same brightness (exposure). When shooting a moving subject, you must be careful since slowing down the shutter speed tends to lead to camera shake or the blurring of subjects.

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Comment from a learner

I tried photographing a fairly stationary copper pheasant in Av (aperture priority AE) mode with the ISO speed set to AUTO, while at the same time adjusting the aperture (f/number) setting. With the aperture wide open, I was able to easily take photos with the kind of blurred background I had wanted to achieve. It's a great photo because the blurring on either side of the point of focus makes the subject stand out.

Camera settings

Av (aperture priority AE) mode + ISO AUTO + Exposure compensation -1

Note: Photos were taken with three different exposures: f/22, f/11 and f/5.6.

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    Turn the dial to select AUTO while pressing the <ISO> button, and then press the <ISO> button again.
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    Turn the dial to set the aperture (f/number)
  • Image
    It is easier to adjust the aperture by looking through the viewfinder
  • Image
    Copper Pheasant, by a learner
    Copper Pheasant, by a learner
    Copper Pheasant, by a learner
    Enlarge

    Aperture value
    f/22
    Shutter speed
    1/400 second
    ISO speed
    ISO6400
    Exposure compensation
    -1
    Focal length
    300mm
    DSLR Camera (APS-C image format)
  • Image
    Copper Pheasant, by a learner
    Copper Pheasant, by a learner
    Copper Pheasant, by a learner
    Enlarge

    Aperture value
    f/11
    Shutter speed
    1/400 second
    ISO speed
    ISO2500
    Exposure compensation
    -1
    Focal length
    300mm
    DSLR Camera (APS-C image format)
  • Image
    Copper Pheasant, by a learner
    Copper Pheasant, by a learner
    Copper Pheasant, by a learner
    Enlarge

    Aperture value
    f/5.6
    Shutter speed
    1/400 second
    ISO speed
    ISO640
    Exposure compensation
    -1
    Focal length
    300mm
    DSLR Camera (APS-C image format)

Message from Mr.Tozuka

The lower the f/number, the greater the blurring of the periphery of the photo. The adjustment range of the aperture (f/number) will vary depending on the lens (See Lesson 2). Lenses capable of shooting with low f/numbers are called "large aperture" or "bright" lenses and tend to be larger.

Aperture value: f/22

Narrowing the aperture (raising the f/number) expands the depth of field, bringing everything from the foreground to the far distance into focus.

Aperture value: f/11

The feathers are clearly in focus and we can tell that the leaves around the bird are blurred more than in the f/22 shot.

Aperture value: f/5.6

In this photo, the eye of the bird is in focus, but there is a slight blurriness to the bird's chest feathers. The leaves around the bird do not stand out.