This article expands on the information in Tip #8 of my book, Pet Photography 101 (pages 19-20). It’s an overview of exposure compensation and auto exposure bracketing in photography.
Exposure Compensation: What it is and How to Use it
One of the most useful exposure controls available on all DSLRs and most point and shoot cameras is Exposure Compensation. Your in-camera meter wants to essentially make everything it sees a medium gray tone (about halfway between white and black), so that means if you are photographing something that has a large area of white in the scene (like a white dog), your image will probably look too dark if you don’t use exposure compensation. You can remedy this by dialing in an exposure compensation adjustment of about +1 EV to +1.5 EV. Conversely, if you have a large area of dark colors in the scene (like a brown or black cat), your image will probably look too light if you don’t use exposure compensation (-.5 EV to –1.5 EV is recommended in this case). Exposure Compensation is also covered in Chapter 3, Tip 28.
Auto Exposure Bracketing: What it is and When to Consider Using it
One of the most useful exposure controls available on most DSLRs and some point and shoot cameras is Auto Exposure Bracketing. Setting this option will tell your camera to take multiple pictures consecutively at different exposure levels. For example, you can set your camera to take a picture with no compensation, then -1 EV, and then +1 EV. When you review your images, you will see three images, all with a different brightness range. Setting your camera to continuous shot mode (as opposed to single shot) is a good idea when using this mode because you may want to borrow elements from one photo (for example, a sky) and paste them into another. This technique works even better when you use a tripod.
Your shooting mode (for example, Aperture or Shutter Priority) will determine whether the camera changes the aperture or shutter speed when it brackets. In most cases, when shooting Raw, I would recommend a +/- 2 EV for AEB. For those who shoot only JPEG, I would recommend +/- 1 or +/- 1.5EV AEB. Though mentioned elsewhere in the book, a major advantage of shooting Raw is that it’s almost like shooting in AEB mode. You can process the same Raw file multiple times and merge the files together to expand the highlight and shadow details in your images.
Some cameras allow you to auto bracket the white balance, and at least one (Nikon), has a feature called “Auto ISO” that allows you to set a maximum ISO (for example, ISO 1200) and optionally, the minimum shutter speed (for example, 1/30 sec.). Your camera will then sense when it does not have enough light to expose a scene properly at 1/30 sec. at your camera’s widest aperture, and it will adjust the ISO up to a high ISO such as ASA 1200.