Yesterday we talked about the Fill Flash Technique, as a useful tool in tricky lighting conditions. Today well talk about another technique called Auto Exposure Bracketing (AEB). So what exactly is Auto Exposure Bracketing? Autobracketing is a feature found on more advanced cameras, mostly, DSLR cameras, but I have seen Autobracketing starting to show up even in some of the high-end point and shoots.
Simply put, AEB is where the camera will automatically take several successive shots (usually a series of three) with slightly different exposure settings. Depending on your cameras AEB settings, the difference between each of the autobracketed shots could be anywhere up to two stops in each direction, in half-stop or one-third stop increments.
The reason you do this is because the camera might have been deceived by the light (too much or too little) available and your main subject may be over- or under-exposed. By taking three differently exposed shots, you are making sure that if this were ever the case, then you would have properly compensated for it.
As an example, say you are taking a scene where there is an abundance of light around your main subject (for example, at the beach on a sunny day, or surrounded by snow). In this case, using Weighted-Average metering, your camera might be 'deceived' by the abundance of light and expose for it by closing down the aperture and/or using a faster shuter speed, with the result that the main subject might be under-exposed. By taking an extra shot at a slight over-exposure, you would in fact be over-exposing the surroundings, but properly exposing the main subject.
Anytime your photographing a subject with tricky lighting or lots of variation between bright and darker areas. Anytime you feel the scene is a challenging one (too much highlights or shadows). For example, sunrise/sunsets are usually better taken slightly under-exposed so using Auto Exposure Bracketing (AEB) here is a great idea.
To sum things up, be sure and use AEB whenever you want to be sure you don't improperly expose a fabulous shot that you may not get the chance to go back and take again. Use AEB whenever you want to be absolutely sure you have the best exposure possible.