Previously I explained your camera’s advanced modes in detail which allows for more creative control over images. This topic can be found HERE. While using any of your camera’s automatic modes such as, P, A, S, or Auto, your camea is deciding the exposure. The process in which your camera does this is called “Metering”. It is taking a measurement of the scene you intend on photographing and deciding how adjust the previously discussed settings in order to get a correctly exposured image.
We have all taken photos where the background was bright and the person you were intending on photographing is a black silhouette. This is just one example of when your camera is not metering the way you intend it to. You may be thinking to yourself, “How does the camera know how bright or dark the image is supposed to be”. The simple answer is that it doesnt. It is programed to always try obtain an image with 18% grey. This is the most common exposure for all situations but really is more college level than I intend on getting into. Just know that 18% grey is the reference point that your camera uses to get what it thinks to be the correct exposure. From here I will tell you that this isnt a perfect formula, but is very reliable in most situations you will be in with your camera. Given that you are not shooting photographs into extremely dark , extremely bright, or extremely hight contrast areas, you wont have any serious issues with your camera’s choice of exposure. That being said, there are many times that you may chose to and knowing a little more about how to adjust your camera’s automatic metering modes will pay dividends towards great looking photographs.
Matrix - On most camera, this is the default/standard mode for the camera’s metering. In this mode, the camera divides the scene into a set number of sections/segments (number varies from on manufacturer to another) that it uses to take exposure measurements. Once this is complete, it will take make a calculation based on an average across the entire frame. This will cause the camera to take a decent exposure in most any situation. However, as stated above, when there is lots of contrasting lighting, this mode will consistently fail to expose correctly.
Center Weighted – In this system, the camera focuses on the lighting at about 60 – 80% towards the center part of the frame/viewfinder. The balance is less and less important as you move out towards the edges. Meaning, the lighting on the edges of the frame/viewfinder makes less of an impact than the center. The one main advantage is the camera will be less likely to be influenced by a small area that greatly varies in contrast when located outside of the center of the frame. This mode is great for photographs where the subject is in the middle of the image.
Spot - With spot metering, only 1-5% of the frame/viewfinder is measured and will typically be the center of the frame. That being said, many photographers will use this mode to select a correct spot to meter for, then recompose by moving the camera after metering. This modes metering area is very accurate and is not effected by other areas of the frame. It also works VERY well for shooting high contrast scenes. One good example would be when shooting a subject into the sun. If the camera were to meter for the background light (sun), the exposure would cause the subject to be very dark. However, if you were to use spot to meter for the subject, you would have a well exposed subject with an overexposed background. Most prefer the background be an incorrect exposure over the subject. After all, the subject is what you are intending to photograph.
In this example I photographed a model car. I chose this car because it was a dark color (black) and it contrasted greatly against the bright kitchen floor. I placed the Matrix, Center Weighted, and Spot overlays over each image so you can see what the camera pattern is as they act as a imaginary camera frame that mimics what I was doing when I took the shot. Just for show. I also placed a little blue dot on the image to show you what part of the frame I was metering for. This really only applied to Spot Metering Mode. The top two images were metered with Spot, and in the first image I metered for the black portion of the model. This caused the image to be over exposed. The second was metered for a very bright portion of the floor and caused the camera to “squint” and under expose the image. The bottom two images look the best in my opinion and were taken with Matrix and Center Weighted modes respectively.
In example 2, I placed four images side by side. The first two images were taken with Matrix and Spot metering respectively. As you can see, the matrix mode did a pretty decent job exposing for the entire scene. However if you really wanted to bring out the bright area of light on the chair, you would need to use Spot. Same with the second set of images. There was so much bright light coming in from the outside that the dark chair just got darker when using Matrix. In the second image, I metered for the actual dark chair which resulted in the background becoming over exposed. This may be an acceptable technique in certain situations.
By understanding how your camera chooses exposures, you can start to manipulate it’s metering modes so that you get the photograph exactly as you want it. Nothing is more frustrating than having a perfect subject and not being able to pull off the shot you want. Hopefully after reading this post, you will have a little more courage in experimenting with your camera’s different metering modes. Please, if you have have any questions….ask =).
Next time I will be explaining your metering window, exposure compensation, and how to use them together.
Las Vegas Photographer