As the name implies: the light meter measures the incoming light. It takes the chosen settings into account and shows whether your photo will be properly exposed, underexposed or overexposed. The light meter can measure light in different ways.
YOUR LIGHT METER IS THE STARTING POINT
You’ve probably seen it before. A bar with – 3, 0 and +3 in it. You know that your photo will be properly exposed if the dot is in the middle, below 0. If the dot is on the left, the minus side, you know that your photo will be too dark. If the point is on the right, the plus side, your photo will be too light. There is one thing to keep in mind: your light meter will translate everything into medium gray. This means that your exposure does not immediately give the best image in all cases, even if the dot is below 0.
For a perfect exposure, it is sometimes necessary to slightly under or overexpose your photo. An environment with many bright parts is automatically made darker and a photo with many dark parts is automatically lightened. Black doesn’t really become black anymore and white doesn’t really become white anymore. This difference is often small, but it is easy to adjust with exposure compensation . With the exposure compensation you can set your light meter to take this into account. So see using your light meter as a starting point, as a basis for the combination of shutter speed, aperture and ISO.
THIS IS HOW THE LIGHT METER WORKS
I want to take a portrait and set my camera manually. The first setting I set is ISO and I set it as low as possible to prevent noise. Then I choose an aperture of f 2.8 for a nice blurred background. I have not yet set the shutter speed, but it is set to 1/8 of a second. You can now see the tip of the light meter at the far right of + 3. If I don’t change this shutter speed, my photo will be completely overexposed. I’m now going to speed up the shutter speed to make the photo darker. You can see the tip of the light meter slowly moving towards the center. You will now see a properly exposed photo. Your camera automatically measures the light when you photograph in automatic mode, aperture priority mode, shutter speed priority mode or P mode.
If you shoot with manual focus, then pay close attention to your light meter. Not all cameras will measure light continuously. You will not see the dot that indicates whether your photo is too light or too dark. In that case, it is necessary to briefly press the shutter release button. The light meter is then reactivated and the dot appears.
Your light meter therefore measures the incoming light, but this can be done in different ways. Which light metering method is the best choice depends on the situation:
MATRIX MEASUREMENT / MULTI-PLANE MEASUREMENT
First of all, matrix measurement, also called multi-plane measurement. This is the most commonly used metering as it is set by default on most cameras. Matrix measurement will also show the best result in most cases. What matrix measurement does is divide the complete image into several planes and measure the light in all these planes. Your camera will then make an average of this. With an evenly lit environment, this measurement works well, but if you have an environment with many contrasts, matrix measurement will have difficulty with this. The exposure of your image can then be disappointing. If so, choose a different light metering or use exposure compensation.
Center metering measures a number of points in your entire image, but looks much more towards the center. The middle is counted more heavily. For example, center measurement is very suitable in situations with a lot of backlight or during concerts and theaters. If you use matrix metering in backlit situations, your subject will quickly become a silhouette. Of course fantastic if that is your intention, but if not it becomes annoying.
Spot metering comes closest to the separate light meters that studio photographers in particular work with a lot. With spot metering you can measure the light very accurately, because it measures a very small part of your entire image, about 3% or 5%. By default, this point is the center, but with certain cameras you can set it to measure at the point where you place the focus point. Spot metering works well for shots with a lot of black or a lot of white or if you want to measure the light on a subject very precisely.
PARTIAL MEASUREMENT / PARTIAL MEASUREMENT
Partial metering is in between center metering and spot metering. Partial metering measures the center of your image without including the rest of the image. Partial metering also measures a much larger part of the center than spot metering. If you have a photo with a clear subject or if you are photographing with difficult light, partial metering is a good method for measuring the light.
In the example below you always see the same environment, but a different light metering method has been chosen for each photo. You can see that there are three completely different results. In this case, the bridge is the darkest point in the image and the sky is the brightest point. It is therefore logical that spot metering has made the photo as a whole considerably lighter, because in this case it measured the light at the darkest point. Center metering measures light across the entire frame, but with an emphasis on the center. Because the sky is the lightest point and is more present than the bridge, center metering makes the photo slightly darker. Matrix metering has a difficult time in this case, because there is a lot of contrast and is exactly between spot metering and center metering.
Which light metering method is the winner? In my opinion, it is matrix metering, because with that you can recover the most in post-processing without too many edits in the highlights and shadows. All in all, an environment with many contrasts remains a challenge for the camera, but fortunately there are other solutions such as shooting in RAW or taking an HDR photo.
You now know everything about light metering and light metering methods. Not sure if your photo has been properly exposed? Then view your histogram ! Via the histogram you can check whether your photo is properly exposed or whether you should underexpose or overexpose your photo more.