Digital Photography Exposure - Aperture PriorityMy preference is aperture-priority exposure because depth of field (both deep and shallow) are important to me, and I can always get a faster shutter speed by paying attention and choosing a wider aperture.
To do this, you have to understand a little about what the metering system is doing and then use exposure compensation. With a little practice, anyone can do that quite quickly and get excellent exposures that are as good as using manual exposure, yet are easier to do.
Note: I am not suggesting that anyone who has a good manual exposure practice change, but I am suggesting that manual exposure is not the only way to get excellent exposures.
How a Digital Camera Meter WorksUnderstand that a meter wants to interpret a scene and make everything middle gray from the exposure. In many scenes, that is fine, but not all scenes have a perfect balance of middle gray tones. The metering system tries to compensate for the emphasis on middle gray by metering multiple points in a scene and making some adjustments unique to those measurements (which is what the metering system is doing).
Still, if a scene is mostly bright (such as a scene with a lot of sky), the metering system will want to make it a middle gray which is darker than it should be. I will typically add plus compensation to such a scene immediately before even taking a picture. If a scene is mostly dark (such as a scene with pine trees filling the image), the system will want to make it middle gray which is lighter than it should be, so compensation on the minus side is needed. Knowing that allows me to interpret a scene right from the start.
DSLR Camera Exposure or Highlight WarningsI typically use the exposure warnings that appear in the LCD review of your shot as an indicator of good exposure. I think it is important that you set your camera so that this review is on longer than the default which is usually way too short (I like 8-10 seconds - you can always turn it off by touching the shutter release button). I adjust exposure compensation either plus or minus until the brightest parts of the photo just start to give the warning or until the warnings just disappear.
It is important that you do not automatically accept an exposure that has no warnings ,as this could mean you are significantly underexposed. When you are adjusting your exposure this way, you are "setting" the brightest parts of the scene as the brightest parts of your photo. This is actually using a part of Ansel Adams classic exposure system, the Zone System, without doing a lot of study and work.
Digital Camera Histogram Is Helpful TooSo I simply set your exposure as best as I can, then take a picture for a test. I will then check my review to be sure my exposure is correct by watching for those blinking highlight warnings. A quick adjustment of exposure compensation and another shot gets the right exposure quickly if the first exposure is off (and often it is correct). With practice, you can actually interpret what you see in the LCD to give a rough idea of exposure (it is not completely accurate, but it can be a start).
For difficult scenes, or when I am just not sure what the camera is doing, I will check the histogram. The important thing about the histogram is that you do not want large gaps at the right side with most of the histogram at the left (which is underexposure and an underuse of your sensor).
A challenge is when you are constantly changing your shot so that the background changes and influences the exposure. For that reason, I pay attention to the shutter speed the camera chooses in order to make a good exposure with the aperture I chose in aperture priority. Then when the scene changes, I quickly shift the camera’s exposure compensation to give me that shutter speed for a specific shot. That way I am not constantly shifting back and forth between manual and autoexposure and my autoexposure is ready for changing conditions.
More information...Rob Sheppard - Outdoor Photographer magazine's editor at large - teaches many excellent online photography workshops at BetterPhoto's digital photography school, including:
About Author / Instructor / Photographer, Rob Sheppard
He is also the author/photographer of over thirty photo books, including The Magic of Digital Landscape Photography, The National Geographic Field Guide to Photography - Digital, and Adobe® Photoshop Lightroom for Digital Photographers Only. He writes regularly for Outdoor Photographer and teaches around the country, including workshops for the Palm Beach Photographic Centre and the Light Photographic Workshops. His Web site for workshops, books and photo tips is at www.robshepppardphoto.com, and his blog on nature and photography is at www.natureandphotography.com.
As a photographer, Rob worked for many years in Minnesota (before moving to Los Angeles), including doing work for the Minnesota Department of Transportation, Norwest Banks (now Wells Fargo), Pillsbury, 3M, General Mills, Lutheran Brotherhood, Ciba-Geigy, Anderson Windows, and others. His photography has been published in many magazines, ranging from National Geographic to The Farmer to, of course, Outdoor Photographer and PCPhoto.
He and his wife, Vicky (married 30+ years), live in the Los Angeles area. They have a son working on his Ph.D. in youth sports and education, and a daughter studying communications/journalism.
Also see Rob's Nature and Photography blog.