Matt explains the ins and outs of bracketing – what it is and how to do it
Bracketing is a useful way to get the shot you want in camera, without you needing to adjust it later in post processing.
The idea behind bracketing is simple: you take one image at a particular group of settings and then two additional images of the same scene, but with one variable adjusted one way for the first image and the other way for the other.
It works as a kind of insurance, in that if the image captured at the standard settings isn’t quite right, one of the other two images may be.
The most common application of bracketing is for exposure, where one image is captured at the camera’s default settings, one image is captured with a slight bias towards underexposure and the final image captured with an equal bias towards overexposure.
The bracketing function is often marked on your camera by the icon of light, medium and dark rectangles, although it may also be marked by the letters AEB which stand for Auto Exposure Bracketing, or simply BKT.
Most cameras allow you to vary the extent of shift for the secondary frames so that they are either slightly under and overexposed, such as by a third of a stop, or altered more significantly, perhaps by a full stop or more in either direction.
You can usually adjust the shift in either direction in 1/3EV-stop increments. The markers underneath the exposure scale move as the level of compensation is adjusted to show how under and overexposed each additional frame is compared to the standard exposure.
There are two main benefits of using bracketing over manually adjusting settings for each image. First, the camera is programmed to take each of the three frames with every press of the shutter-release button, which saves you time and effort as you don’t need to make a separate adjustment before each frame.
You simply press the shutter-release button to capture the standard frame, press it again to capture the overexposed frame and one final time to capture the underexposed frame. Some cameras may even do all three at once.
Second, as you are able to do this automatically with nothing more than a press of the shutter-release button, you stand to capture the scene similarly in each frame. So, even if your subject isn’t completely static, the fact that you’re capturing it quickly should result in three similar images.
Camera manufacturers have applied the principle of exposure bracketing to a range of other camera settings. One of these is white balance, which allows you to capture one standard image, one image bearing a slightly warm tint and one with a slightly colder one. This is particularly useful for situations under artificial lighting sources, which auto white-balance systems often find problematic.
Other bracketing options include flash bracketing, which works in the same way as exposure bracketing but for flash power, and sensitivity bracketing, which can be useful if the standard image results in slight camera shake or blur through subject movement. Many cameras also offer bracketing for dynamic range optimisation and for different colour and processing effects.
