Auto exposure bracketing explained

Auto exposure bracketing (AEB) is a feature on Canon cameras where the camera can be configured to take a picture at the metered exposure setting, plus additional pictures that are over and or underexposed relative to the metered reading. Mostly the feature give photographers options in post production to merge different parts from the different images – so called high dynamic range imaging (HDR). Canon cameras allow bracketing to be set in 1/3-stop increments from 1/3 EV to 3EV. With a 7-stop bracket that is an 18-stop range.

All Canon SLR cameras have AEB

All of the Canon DSLR cameras feature AEB. Carried over from the film era it was usually three pictures that were taken, one under the metered exposure, one at the metered exposure, and one over the metered exposure. Probably since memory card sizes were not so big initially digital cameras kept the three shot auto exposure bracketing range.

Combining exposure compensation and exposure bracketing

Exposure compensation and auto exposure bracketing combined

Sometimes for HDR images it is required to use exposure compensation for the meter reading, this is combined with the bracketing function. So if the exposure compensation is set to -1EV then the bracketing is set to 1EV increments the three shots taken will be -2EV, -1Ev and 0EV from the metered reading.

Professional & advanced cameras extend auto exposure bracketing

The top of the range professional cameras have extensive customisation. It is via custom functions (C.Fn) or personal functions (P.Fn) that the number of shots taken as part of a bracketed sequence can be changed. Most recently due to the interest in high dynamic range imaging (HDR) the ability to choose the number of bracketed frames has spread further down the model line-up.

Cameras with more than 3-shot auto exposure bracketing

Advanced cameras can change the number of bracketed shots

Camera	AEB, number of shots	C.Fn / P. Fn
EOS-1D / EOS-1Ds	2, 3, 5, 7	P.Fn 08
EOS-1D Mark II / EOS-1Ds Mark II	2, 3, 5, 7	P.Fn 08
EOS-1D Mark II N	2, 3, 5, 7	P.Fn 08
EOS-1D Mark III / EOS-1Ds Mark III	2, 3, 5, 7	C.Fn1-6: Number of bracketed shots
EOS-1D Mark IV	2, 3, 5, 7	C.Fn1-6: Number of bracketed shots
EOS-1D X / EOS-1D C	2, 3, 5, 7	C.Fn1: Number of bracketed shots
EOS 5D Mark III	2, 3, 5, 7	C.Fn1: Number of bracketed shots
EOS 70D	2, 3, 5, 7	C.Fn1-5: Number of bracketed shots

Not just AEB – auto white balance bracketing too

Changing the number of auto exposure bracketed shots, also changes the number of shots that are taken when using auto white balance bracketing. This can result in the camera buffer becoming full very quickly since the camera creates multiple image files from each exposure with different white balance settings.