One of the most useful techniques in photography is called bracketing, in other words, taking multiple photos of the same subject with different camera settings. Normally, bracketing is about changing your exposure: one photo at the meter’s recommendation, plus one under and one over. But exposure is not the only variable at play here.
Why Bracket Photos?
Bracketing means you capture a sequence of photos while changing your camera settings from shot to shot. This means you end up with two or more photos of the same scene, with only a couple of differences in each shot.
Exposure bracketing is the most common kind of bracketing in photography, will usually ending up with one photo that is too dark, one that is too bright, and one with a correct exposure. But bracketing the focus distance will resulting in one photo that is front-focused, another that is back-focused, and one that is accurate.
Some people consider bracketing takes up memory and wastes time. Especially if one knows what settings needed for an image, so, why bracket shots? There are two important reasons why bracketing is beneficial in photography.
1. Playing it Safe
Firstly, no matter how experienced a photographer the camera settings may be wrong. The three planned exposures, an overexposed, an underexposed, and one correct exposure will not always materialise that way. In their place, one may be extremely underexposed, another significantly underexposed photo, and another that is correct.
It is difficult to perfectly judge exposure in the field, especially in high-contrast light or other problematic conditions. Bracketing is a way to reduce potential problems by taking safeguards against common errors people generally make. Particularly for important potential one-time shots, it is a low-risk, high-reward procedure.
2. Merging Photos
Sometimes, bracketing is the only way to capture the photo required. For example, if shooting an ultra-high-contrast scene, one photo may not achieve the required results. A single image at normal exposure will lead to highlights that are too bright, and resulting in dark, noisy shadows.
Occasionally this sort of problem can be rectified using a graduated ND (neutral density) filter, but the more practical option is to do things digitally. Take an underexposed photo so the highlights look good, plus an overexposed photo so the shadows are right. Then, combine the best parts of each photo into an HDR or luminosity blend.
Of course, one can go beyond a two-photo blend, by using three photos. For my part, I do not like blending exposures with more than 2/3 stop of exposure between them because the transition areas can look grainy.
How to Do Exposure Bracketing
The actual process of exposure bracketing is easy. In any semi-automatic mode, change your exposure compensation from shot to shot. In manual mode, change any of the three settings manually: aperture, shutter speed, or ISO.
Most decent cameras today allow the setup of automatic bracketing within the menu. When enabled, the camera will automatically change settings from shot to shot rather than making manual modifications. Some cameras only allow exposure bracketing, while others have bracketing options for JPEG settings, white balance, and other camera settings. Although bracketing is found in the menu, most modern cameras frequently assign a custom button to access this option quicker, while others have a specific bracketing button.
Which Exposure Setting Should You Bracket?
Earlier, I stated that it is important to choose your bracketing setting carefully. Even though you can bracket shutter speed, aperture, and ISO just as easily as one another.
Aperture - since aperture affects depth of field it can be the worst setting to bracket. Creating an HDR from f/4 - f/5.6 - f/8 will result in an odd image, with unnatural transitions having blurry to sharp regions looking odd. A five-image bracket can be worse.
ISO – neither is adjusting the ISO setting, since each shot at different ISO settings will have distinctive levels of image quality. Anyway, an HDR shot at ISO 400, 800, and 1600 will not be improved over a single ISO 400 image.
Shutter Speed - the exposure setting is the setting one considers adjusting first. Especially if shooting from a tripod, and the subject is not moving. However, in scenes with quickly moving subjects and the potential for motion blur, the flexibility of bracketing shutter speed is limited. In action shots, ISO is often the better choice.
Focus bracketing is easier than exposure bracketing since there is only one setting under consideration: focus distance. Here, the goal comprises of focus stacking the images in post-processing later, like a group photo where everyone needs to be sharp but is unsure where to focus for the best result.
Focus bracketing works best when overlapping the depth of field from shot to shot. But, if the steps are too wide, you can end up with an odd: sharp, blurry, sharp, blurry, sharp, etc.
So, when bracketing focus manually, take photos with smaller focus increments, and if possible review each photo afterward to check that the transitions are smooth. However, previews on a camera’s rear LCD look different than full-size images on a high-resolution monitor.
These days, many cameras today have a built-in focus stack feature to simplify this process. Focus on your nearest subject, tell the camera how many photos to take, and select a step size. I still recommend selecting lower increments than one might expect. It is also a good idea to test these features beforehand so you know how to use them correctly.
In theory, bracketing can refer to pretty much any variable in photography. You can bracket white balance, JPEG settings, long exposure noise reduction, flash settings, focal length, and much more.
If unsure what depth of field required, it is worth bracketing the aperture. Or, for a Milky Way photograph, consider using different ISO and shutter speed settings to obtain the best combination of noise performance and minimal star trails.