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19 Jul 2024

Auto Exposure Bracketing (AEB)

Term: Auto Exposure Bracketing (AEB)
Description: Auto exposure bracketing (AEB) is a camera feature that involves capturing multiple images of the same scene with different exposure settings. AEB typically involves taking three or more images: one at the camera's default exposure setting, one underexposed, and one overexposed. The underexposed image will be darker than the default setting, while the overexposed image will be brighter. This technique is often used in photography to ensure that at least one of the images captures the scene with the correct exposure. AEB can be useful in situations where the lighting conditions are difficult to predict, such as in high-contrast scenes or when shooting at sunrise or sunset. Additionally, AEB is commonly used in post-processing techniques such as HDR (High Dynamic Range) photography, where the multiple images with different exposures are merged to create a final image with increased dynamic range and more accurate representation of the scene.

Also see our definition of bracketing.

Boosting Dynamic Range by Combining Exposures

In previous articles we went over fundamental concepts such as high dynamic range and stops of light. Now that we understand these concepts, we are ready to dive into learning techniques for capturing images for our final HDR product. In this article, we will introduce the technique of bracketing to broaden the dynamic range captured by your camera.

BROADEN THE DYNAMIC RANGE OF YOUR CAMERA

In order to expand the dynamic range within your images, you can either:

1. Buy a more expensive DSLR that can capture a broader dynamic range, or

2. Keep your camera and combine multiple exposures at different brightness levels to expand dynamic range.

Most likely, the second option is more appealing and cost-effective. In fact, you can get fantastic images by combining multiple exposures without having to buy a new camera. This technique is called bracketing, and it isn’t as complicated as it may sound. Many DSLR cameras have a built-in function called “Automatic Exposure Bracketing” (AEB) that does the bracketing procedure for you. Most importantly, it does it quickly.

AUTOMATIC EXPOSURE BRACKETING

The AEB function allows us to tell our cameras to capture a group of images that differ by a specific exposure value spacing. You can customize the spacing to the value of your choice. In our studio, we most commonly set our cameras’ AEB to what we refer to as a three-frame, two-stop bracketed sequence.

For example, here is a sequence of images with those particular specified settings:

A middle exposure set at 0 EV,

hdr-aeb-auto-exposure-bracketing-examples-0001

a dark exposure set at -2 EV,

hdr-aeb-auto-exposure-bracketing-examples-0002

and a bright exposure set at +2 EV.

hdr-aeb-auto-exposure-bracketing-examples-0003

We find that this particular setting generally gives us the right amount of stop spacing for three images to combine for our HDR image. Note that if you are producing an HDR with people as subjects, the lightest exposure is usually set ideally for their skin tones, but may still need to be adjusted.

To show you an example of a finished product, here is the final produced HDR image from the previously bracketed shots:

hdr-aeb-auto-exposure-bracketing-examples-0004

As you can see, the dynamic range of this image is more broad than any of the previous images by themselves. This combined image shows detail in the shadowed areas, such as the rocks, and also in the highlights, such as the sky.

CAMERAS WITHOUT AEB

If your camera doesn’t have an AEB function, you will have to perform this task manually. While this can be done, there are a few problems that can occur when trying to shoot a bracketed sequence with a camera that doesn’t have AEB.

The first problem is time. If you are trying to capture three images in a row with different exposures, it will take you probably around 10 seconds, and that is if you are fairly fast. If anything is moving within your frame, it will cause a ghosting effect or parts of your image when you layer all 3 shots.

The second problem for dialing the settings manually is the fact that you have to constantly touch your camera to adjust the settings. Handling your camera, even in the slightest, can easily change or shake the the frame of the image. Once again, when you layer these shots you will lose detail and quality in your final image.

So, while it is possible to dial in your bracketed settings manually, you are always going to be better off using your camera’s AEB.

CONCLUSION

At this point, you should have a basic understanding of exposure bracketing. We are going to be learning to combine these bracketed images to produce our final HDR image, which will be covered in a later tutorial.

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