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In photography, bracketing is the general technique of taking several shots of the same subject using different or the same camera settings. Bracketing is useful and often recommended in situations that make it difficult to obtain a satisfactory image with a single shot, especially when a small variation in exposure parameters has a comparatively large effect on the resulting image. Autobracketing is automatic bracketing by using a setting on the camera to take several bracketed shots (in contrast to the photographer altering the settings by hand between each shot).


[edit] Types of bracketing

[edit] Exposure bracketing

Without further qualifications, the term bracketing usually refers to exposure bracketing: the photographer chooses to take one picture at a given exposure, one or two brighter, and one or two darker, in order to select the most satisfactory image. Many professional and advanced amateur cameras, including digital cameras, can automatically shoot a bracketed series of pictures. Exposure bracketing is indicated when dealing with high-contrast subjects and/or media with limited dynamic range, such as transparency film or CCD sensors in many digital cameras.

When shooting using print film, the person printing the pictures to paper must not compensate for the deliberately underexposed and overexposed pictures. If a set of photos are bracketed but are then printed using automated equipment, the equipment may assume that the camera or photographer made an error and automatically "correct" the shots it determines are "improperly" done.

[edit] Focus bracketing

A series of images demonstrating a focus bracket. The image on the left shows a single shot taken at f/11 with the features of the spider closest to the camera. The center image shows the features farthest from the camera. The image on the right shows focus stacking: a sequence of 8 incrementally focused images of the spider assembled to make a composite image in Photoshop. The magnification had to be changed by a factor of 0.5% between each image (first image at 100%, next at 100.5%, next at 101%, etc.).
Cracked mushroom animation The composite created from same
An animation of the fourteen shots used to create a picture using focus bracketing (on left), next to the final image (right)

Focus bracketing is useful in situations with limited depth of field, such as macro photography, where one may want to make a series of exposures with different positions of the focal plane and then choose the one in which the largest portion of the subject is in focus, or combine the in-focus portions of multiple exposures digitally (focus stacking). Focus stacking is challenging, in that the subject (as in all brackets) must stay still and that as the focal point changes, the magnification (and position) of the images change. This must then be corrected in a suitable application by transforming the image.

[edit] White balance bracketing

White balance bracketing, which is specific to digital photography, provides a way of dealing with mixed lighting by having the camera make several images with different white points for one exposure taken, often ranging from bluish images to reddish images.

White balance bracketing doesn't require actual multiple exposures, but merely reprocesses the same raw sensor data with different white balance settings. When shooting in a camera's RAW format (if supported), white balance can be arbitrarily changed later, so white balance bracketing is unnecessary.

[edit] Flash bracketing

Flash bracketing is a technique of working with electronic flash, especially when used as fill flash in combination with existing 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.

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