The camera meter...
Nearly all cameras today have automatic metering modes in addition to the manual metering mode. There are usually three auto exposure modes.
- Aperture Priority: You choose the aperture, and the camera chooses the appropriate shutter speed for the exposure.
- Shutter Priority: You choose the shutter speed, and the camera chooses the appropriate aperture for the exposure.
- Program: The camera chooses both shutter and aperture. You have very little control. I do not usually recommend using the Program mode unless it’s literally your first day with a serious camera.
Different cameras have different ways of indicating a “correct” exposure. Some use a match-needle. Others use LEDs to indicate under, over, and correct exposure. Still others, mainly new cameras utilizing LCD displays, use an analog scale that shows a plus and minus range. (See the illustration below). Zero means “correct” exposure and the plus side means “over exposed.” Likewise, the minus side means “under exposed.
Most new cameras also give the photographer a choice of metering patterns. These include spot metering, center-weighted metering, and evaluative, also known as matrix (or evaluative) metering. Be sure to read your camera manual so that you know how to set and use your metering system.
In most cases, I usually recommend setting up a camera with matrix or evaluative metering. These modes evaluate the entire scene, compare levels of brightness, and then, use proprietary algorithms, to set a “correct” exposure.
Most of the time, this approach works just fine. The camera will correctly expose your photo based on the settings you’ve chosen. However, you can still take even greater control of exposure. The key to advanced exposure technique is paying attention to the tonality of an entire scene, the tonality of the primary subject, and the size of the subject in the frame.
If you can do this regularly, you’ll soon be setting exposure accurately and getting good results nearly every time. Let’s look at a few common situations.
Advanced Metering Modes
Spot meters, as the name implies, sample a very small portion of the viewfinder. If you know how to use a spot meter, you can evaluate an entire scene and precisely control exposure.
Center weighted meters evaluate the entire viewfinder, with most of the measurement coming from the center portion. Depending on your camera, this center portion is given about 75 or 80 percent of the “weight” in determining the exposure, with the other 20 to 25 percent coming from the rest of the frame. In some cameras, you can specify this percentage via a custom function.
Evaluative or matrix meters divide the entire scene into zones and evaluate the relative brightness between different sections of the scene. Then, using proprietary algorithms, the camera determines the “best” exposure for the situation.
How I Meter Most Scenes
I primarily photograph birds. Many avian subjects are medium-toned, neither light nor dark. However, some are not medium-toned.
For example, if you want to make a picture of a great egret, consider this: Great egrets are white and they can be found in bright reflective water. A scene like this often fools the meter into thinking that there is more light than there actually is. You’ll need to “overexpose” it to make it come out lighter than medium. Remember the camera meter wants to make everything medium gray. So unless you want your white bird to come out gray, add exposure compensation.
Egret exposed according to the camera's automatic settings...
In this case, if you adjust your camera controls so that the meter indicates “0,” the subject will come out medium, which will be too dark.
If you set your controls so that the meter indicates +1.5, or even +2, then the subject will come out one and a half to two stops lighter than medium, or just right.
Egret with plus 1.5 stops of exposure...
Notice I said one and a half to two stops lighter than medium, not one and a half to two stops lighter than the subject really is. This is where people get confused. Beginners often think that by setting the meter to +1, the subject will come out one stop too bright. No. It will come out one stop lighter than medium.
To make sure you understand how the meter in the camera works, take this simple test. Do you know the answer to the following question?
If you stand in a room where the wall on your left is white, and the wall on your right is black, and you use the camera's matrix metering mode to gauge exposure, what color will the picture come out when you point at the white wall? How about the black wall? If you answered gray, then you have it. If you don't understand this then shoot it for yourself. Remember, your camera meter is trying to make everything 18% gray. So if you shoot at the white wall, the camera will stop down to make it gray. If you shoot at the black wall, the camera will open up, to make it gray. I know it seems counter-intuitive but it works.
More Advanced Metering Techniques
Using Another Object for Metering - Instead of metering your subject, you can use something else in the scene that has a good range of mid-tones. For example, find a medium-toned rock, tree bark or grass in the scene.
You can preset your exposure based on something that’s of a known medium tonality and in the same light as your subject.
Remember, if you get the medium tonality right, the rest of the picture will fall in to place, providing everything is in the same light. This is especially helpful if the subject is small in the frame.
When photographing in even light, if you correctly meter one tonality, all the rest will fall into place. This means if you have a medium-toned animal standing next to bright yellow autumn foliage, you can either meter the animal and set the meter to “0,” or meter the foliage and set the meter to “+1.” Both methods will yield the same setting and same exposure.
Remember, in general, you need to add light (overexpose) for light-toned subjects, and subtract light (underexpose) for dark-toned subjects. Deciding just how much requires practice.
The following are some tonalities found in the natural world. Use these as guidelines to get started.
Common Exposure Compensation Values:
- “The following are some tonalities found in the natural world. Use these as guidelines to get started. Common Exposure Compensation Values
- Yellow leaves (fall color): +1 (yellow is generally about one stop lighter than medium)
- Yellow flowers (daffodils, etc.): +1
- Orange flowers, pumpkins: generally medium (0)
- Bison: -1 to -1 1/3
- Green grass: -2/3 to medium (0) depending on the season
- Dry grass: +2/3 to +1
- Tree bark: generally medium (0)
- Deer (most any species): medium (0)
- Evergreen trees: -2/3
- Snow: +1 1⁄2 to +2
- Reds: medium to –1 depending on how deep the red
- Desert sand: generally +1
- Mountain lion: medium (0)
- Palm of your hand: +1”
Learning the tonalities of subjects in the natural world, and exposing for those tonalities, will give the results you want.
ABOUT THE AUTHOR
Scott Bourne is President of US and Chinese Operations at Skylum Software (Makers of Luminar & Aurora HDR,) an Olympus Visionary, a professional wildlife photographer, author, lecturer and a signed Master Photographer at Studio of Masters, China who specializes in bird photography. He was one of the founders of This Week In Photo, founded Photofocus.com and is co-founder of the Photo Podcast Network.
Scott is a regular contributor to several photography related blogs and podcasts and his photography has appeared in more than 200 books and magazines. He is a trainer at both ThinkTapLearn and lynda.com, and is the author of 11 photography books.
Scott is available to speak to your birding group, photography group and for private bird photography workshops. For more information on engaging Scott as a speaker or workshop leader, or for image licensing and print information, e-mail firstname.lastname@example.org.)