A Quick Introduction to Automatic Exposure Bracketing

April 29, 2016

A Quick Introduction to Automatic Exposure Bracketing

A couple of weeks back, we did a blog post on dealing with difficult exposure situations using Exposure Compensation.

In this post, we'll talk about another way to get good exposure when lighting is tricky land that's by using Automatic Exposure Bracketing, also called AEB.

What is Exposure Bracketing?

Before we talk about Automatic Exposure Bracketing, it's important that you first know about bracketing.

Bracketing is a term used in photography that refers to taking multiple shots of the same scene–usually three–while varying a particular camera setting with each shot. Specifically, when you do exposure bracketing, you take one shot using the camera's suggested exposure settings, then another shot underexposing the scene and a third shot overexposing the scene. Usually you under- and overexpose by equal amounts.

For example, consider the three images below.

The center shot uses the exposure settings suggested by the camera's internal sensor. The shot on the left underexposes the scene by one stop. The shot on the right overexposes the scene by one stop.

A Quick Introduction to Automatic Exposure Bracketing

Bracketing is a easy way to make sure that you have properly exposed image, especially when you are shooting in a difficult lighting situation. So bracketing can be used when you are unsure of what exposure to use in a particular scene but you want to be certain of getting the shot.

Bracketing also lets you capture a scene that's beyond the dynamic range of your camera. A high dynamic range (HDR) scene has lots of both very bright areas and very dark areas. Your camera can't capture detail in both.

But by bracketing exposure and shooting images at different exposures settings, you can capture detail in the highlights in one shot and the shadows in another. Then you can bring those shots to together to create a single photo using image software.

We'll talk about this process in detail in a later blog post.

Automatic Exposure Bracketing

One way to do exposure bracketing is to do it manually. This mean that you take a series of shots, dialing in a different exposure for each.

But that takes time.

Instead, most DSLRs and many of the more advanced compact camera systems include a feature called Automatic Exposure Bracketing, or AEB, which automates the process.

The symbol for AEB typically looks something like this:

A Quick Introduction to Automatic Exposure Bracketing

Or you may see it simply labeled AEB or BKT

Depending on your camera model, you may be able to activate AEB from a button on the camera body. Otherwise, you will need to dive into the menu system to access the feature.

How do you use AEB?

You need to check your user manual for the specifics of using Auto Exposure Bracketing on your particular camera.

In general, though, AEB is easy to set up.

Turn AEB on

  • On some cameras, the feature is activated by pressing a button on the body of the camera. Look for a one labeled either AEB or BLK.
  • If there isn't a button, you'll need togo into the camera's menu system to switch AEB on.
    A Quick Introduction to Automatic Exposure Bracketing

Adjust the AEB settings

With AEB turned on, you need to adjust the settings to your preferences.

  • Some cameras give you an option to choose how may bracketed shots you want to take, usually from 3-9.
    A Quick Introduction to Automatic Exposure Bracketing
  • You also need to set the amount of under- and overexposure for each image. This can usually range from 1/3 to 2 stops.
    A Quick Introduction to Automatic Exposure Bracketing

Activate Drive Mode

Now that you have AEB activated and the settings adjusted, you can take a series of bracketed shots. To do this, you need to press the shutter button for each individual shot.

But there's an easier and faster way.

By turning on your camera's Drive mode (sometimes called Continuous Shooting or Burst mode), you can shoot all the bracketed shots in one continuous burst as you hold down the shutter button.

You'll need to check your user manual to see how to switch your camera to Drive mode, but it's usually done via a dial or level on the camera body.

How does AEB work?

We know that Auto Exposure Bracketing takes a series of images, varying the exposure with each. But how exactly is the exposure changed? What setting of the exposure triangle–aperture, shutter speed or ISO–is changed to vary the exposure?

The answer to that depends on the shooting mode that you are using when capturing the bracketed images.

By the way, for more on how each of these modes work, check out our earlier post Understanding Your Camera's Shooting Modes

Program Mode

When shooting in Program mode, the camera will vary the shutter speed to change the exposure for bracketing.

Aperture Priority Mode (Av)

When shooting in Aperture Priority mode, the shutter speed changes in Automatic Exposure Bracketing.

Shutter Priority (Tv)Mode

When shooting in Shutter Priority mode, the aperture changes to create under- and overexposed images when using Automatic Exposure Bracketing.

A Couple of things about using AEB with Shutter Priority

There are a couple of issues to be aware of when using Automatic Exposure Bracketing in the Shutter Priority mode.

  • Since the aperture changes to create the different exposure scenarios in Auto Exposure Bracketing, the depth of field for your image will also change. For this reason, AEB has limited usefulness when working in Shutter Priority mode.
  • You can run into issues when using AEB in Shutter Priority mode if your "normal" exposure requires the aperture to be set at or near the

    Consider an example.

    Say that you are shooting with a lens that has a maximum aperture of f/4.0. You are using Shutter Priority mode and have set the shutter speed to 1/125th of a second. The camera's internal sensor suggests an aperture of f/4.0. So the recommend exposure is f/4.0 at 1/125th of a second.

    Now you want to use the camera's AEB feature to bracket by 1 stop. Remember that when using Shutter Priority, the aperture setting varies for the different exposures when using AEB.

    When the shutter button is pressed, the camera starts shooting the 3 bracketed images. The first image is taken at the recommended exposure of f/4.0 at 1/125th. The second, underexposed shot is taken at f/5.6 at 1/125th of a second. The third, overexposed shot should be taken at f/2.8 at 1/125th of a second. But the lens can't open that wide and so the camera ends up taking what should be the overexposed shot at the same exposure settings as the "normal" shot, using the camera's recommended exposure settings.

Manual Mode

Some older model cameras don't allow the option of using AEB while shooting on Manual mode. If that's the case, you will have to resort to bracketing manually. Most newer model cameras, however, do allow AEB while in manual mode; in this case, the bracketing occurs by varying the shutter speed.

For More Information…

What is Exposure Bracketing?

Why I always use Auto-Bracketing

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