This week’s lesson is about the camera’s light metering modes. If you want to get that perfect exposure, you need to take control of the light meter and finely tune your settings. In this blog post we’ll cover the basics of in-camera light metering and the three different light metering modes.
In-camera light meter
Most cameras have an in-camera light meter that meters reflected light. The camera uses reflected light to calculate how much light is actually present in the scene. Simply put, the camera checks how bright a scene is, and uses that to figure out the proper exposure.
All cameras have a default “proper” exposure, which is an 18% grey image. Cameras don’t actually see color, only shades of grey. This default setting works for the majority of scenes, as the 18% grey is actually a result of years of testing and experiments. For a camera the proper exposure is when the result is an image that has the most 18% grey.
But sometimes that default setting is wrong. The camera always strives to get the 18% grey tone, which means that it will try to turn the black background into a greyish background just to achieve the 18% quota. And we don’t want that.
This is where light metering comes into play. By using a different light meter we tell the camera which part of the scene we want to properly expose. We don’t actually care about the rest of the scene, only our subject. So if you only meter your subject, the camera will make sure that only your subject is at 18% grey. The rest of the scene will not matter. This means that the black background won’t affect the exposure level.
Below are the three light metering modes that will help in getting a proper exposure for your subjects.
Matrix metering mode
This is the default setting. The camera meters the whole scene and tries to set an exposure level that will work for the majority of the scene. The problem is that every manufacturer uses a different algorithm to get the proper exposure. So you’re putting your trust in an engineer in some factory. The matrix metering mode works well when you have an “average scene”, a scene that has low contrast and consists of evenly bright and reflective subjects.
Center metering mode
The camera only meters the center portion of the scene, and neglects the rest of the scene. This is a hybrid between the matrix metering scene and the spot metering scene. It works well when you have a subject that covers a substantial portion of your scene and it needs to be properly exposed. In my opinion the center metering mode offers the best balance between control and ease of use, so I use this metering mode about 90% of the time.
Spot metering mode
This is the most precise metering mode. The camera takes only a small portion of the scene and only meters that. Spot metering is very useful in contrasty scenes, where the subject is too small to use the center metering mode. This is the most “extreme” metering mode, because it is very specific. Light metering a person’s dark hat will produce a different exposure level than metering their forehead. It has its uses, but be mindful on what you’re metering.