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10 – Aperture

1 – Introduction

The intensity of the light reaching the sensor is controlled by varying the aperture.

The aperture is an iris-like mechanism in the lens.

Lens opening, f/stop, and diaphragm, are synonyms for aperture.

The numbers used to designate aperture are confusing:

f/4 f/5.6 f/8 f/11 f/16 f/22

Use this mnemonic to help remember what the numbers represent:

The bigger the number, the less light reaches the sensor.

2 – Aperture-priority Exposure Mode

You can set the aperture by using the aperture-priority exposure mode.

In this exposure mode, you change the aperture, and the camera selects the shutter speed.

On Nikon cameras, and many others, this mode is called A.

On Canon cameras, the mode is called Av.

Advantages

If you're using the aperture-priority exposure mode, you'll be more aware of depth-of-field.

Depth-of-field is the area in front of—and behind the subject—that's in focus.

We'll cover depth-of-field later.

3 – Flower & Face Icons

Flower Icon

If your camera has a flower icon on the exposure-mode dial, the camera will use the smallest possible aperture.

The depth-of-field will be larger-more will be in focus.

Use the flower icon when doing:

• A close-up

• A portrait in which you want the background to be more in focus.

Face Icon

If your camera has a face icon on the exposure-mode dial, the camera will use the largest possible aperture.

The depth-of-field will be smaller—less will be in focus.

Use the face icon when doing:

• A still life in which you want the background to be more out-of-focus

• A portrait in which you want the background to be more out-of-focus.

4 – Point-and-shoot Cameras

The aperture on your camera goes from about f/2.0 to about f/8.

Unfortunately, even at f/2.0, there's a lot of depth-of-field.

Your camera doesn't have smaller apertures, such as f/11, f/16, and f/22.

That's because the diffraction would be too great with these small apertures.

Because they have so much depth-of-field, point-and-shoot cameras:

• Excel at doing close-ups.

• Are not as good at doing portraits with out-of-focus backgrounds.

5 – Scene Modes

Many cameras have scene modes, often designated by SCN on the exposure-mode dial.

There may be scene modes for close-ups and for portraits.

Next, we'll look at how shutter speed controls the duration of the light striking the sensor.