Digital imaging: Bracketing

Definition and explanation

Before describing the different types of “image merging” workflows, I will explain some terms that I will be using through this series of posts. Today I will explain the meaning of bracketing.

Bracketing consists in acquiring a series of images with different camera settings. The word bracketing comes from the idea that we have a target value for the setting, say exposure, and we acquire images with this setting and settings both at slightly large and slightly smaller values (bracketing both “sides” of the target). At least three images need to be acquired, but in some exceptional cases even hundreds images are acquired.

Bracketing is an old term and old idea, which of course can be used also with film cameras. Some automatic film cameras and advanced digital cameras can automate bracketing, at least for some parameters. Bracketing can also achieved by manually changing the settings through the acquisition of a series of images. Examples of parameters for which bracketing is frequently used: exposure, focus distance, and white balance. In the case of exposure, bracketing can be achieved by bracketing on aperture, shutter speed, or ISO setting.

The most basic approach is to just choose the best image from the bracketed series, and use it. What I will discuss in future posts in the merging of a series bracketed images into a single composite image which is “better” than any of the individual images.

Examples

Some examples of bracketing on different image acquisition parameters. Click on the thumbnails for a higher resolution image.

Focus

 

Focus bracketing (far)
Focus bracketing (centre)
Focus bracketing (centre)
Focus bracketing (far)
Focus bracketing (near)

Exposure

Exposure bracketing (+2EV)
Exposure bracketing (+2EV)
Exposure bracketing (+0EV)
Exposure bracketing (+0EV)
Exposure bracketing (-2EV)
Exposure bracketing (-2EV)

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