When we want to capture a subject, we usually take a single photograph, but not always. With the advent of digital editing software like the famous Photoshop, you can group multiple shots into one single image in order to obtain a desired effect. Of course, I’m talking about situations where the subject is stationary, such as landscapes and still life, but more rarely you can use a bracketing technique with human or animal subjects. There are different bracketing modes: exposure bracketing, focus bracketing, flash bracketing, white balance bracketing.
- Usually on professional and semi-professional cameras, there is an option to activate the exposure bracketing mode. This kind of bracketing is certainly the most widely used and it’s very easy since we have this simple built-in function. Using the camera with this mode active, it is possible to take multiple shots at different exposures, varying the shutter speed. If we work in Av or Tv (or any other semi-automatic mode), the camera will take the first picture with the correct exposure (“0″ on the light meter), then an underexposed picture and finally one overexposed. We can decide how much underexpose and overexpose the shots in the bracketing mode menu. In some cameras, especially Nikon, there is even the possibility to set five different exposure instead of three. Obviously, if the first shot is underexposed by two stops (-2) and the second by one stop (-1), the overexposed shots will be +1 and +2. I have never seen in any camera with the possibility to create an unbalanced bracket, and quite frankly it would not make any sense.
To use this function at its best, you should also enable continuous shooting mode, which allows you to photograph several times without releasing the shutter button, so to minimize any movement of the camera and the subject.
What is the exposure bracketing function for? You can use it just to have more pictures at different exposures, to be sure you get what you want, but it is much more used to create HDR photos. Without going into details that we will see later, you can combine the information contained in the three or five pictures to obtain a composite image with high dynamic range (HDR = High Dynamic Range) using dedicated software.
In the picture, you can see an example of an HDR image obtained with this technique.
- The second type of bracketing is the focus bracketing. It is not an automatic function of the cameras so it is more difficult to use. It is widely used in macro photography, where the depth of field is reduced to a few millimeters. To obtain a focus bracketing you need to take more photographs with a slightly different point of focus from time to time, and join them together in post-production creating a deeper depth of field image.
First of all, set all the parameters and shoot a picture focusing at one plane using the MF, then refocus on the next plane and shoot another frame. The operation must be repeated several times until you have focused on the entire portion of the image you care about. In post-production, you need to load files into one single composition and join them manually using layer masks.
- The flash bracketing is a technique rarely used in common shots, as it requires the use of an external flash unit (not integrated with the camera).
The external electonic flashes have better performance than integrated flash and have the ability to handle the power of the flash of light. The amount of light provided by the flash is varied in a bracketed series in order to find the most pleasing combination of ambient light and fill flash. The final effect is comparable to that of the exposure bracketing because the difference between shots is their brightness, but the use of the flash bracketing technique is quite different. Taking pictures with flash is always complicated, and this technique can be useful mainly to decide what amount of flash light is desired.
- The white balance bracketing can be used in the same way. You can take several photographs, changing the white balance, to find the best solution in term of temperature and tint.
And the list does not finish here. You can potentially use the bracketing technique with any of the parameters present in your camera, for example by modifying the sensitivity of the sensor you will obtain an ISO bracketing. The point is that you have to think if and how this may become a useful tool in order to solve a technical problem, to create a wonderful composition or simply to capture the shot you want.