If you’re new to photography, you’ve only had your camera for a short time and you’ve already browsed through your camera’s user guide, chances are that you’ve seen the notions of exposure metering appear somewhere.
You have probably already heard about the notion of exposure in photography? It is simply the amount of light in a scene that will be captured by the sensor of your body and will determine the brightness of the picture. You’re going to tell me, that’s all very well, and so what? It is important to know that your camera does not determine the brightness of a scene randomly…
This is where metering modes come into play. There are basically three different metering options that your camera will be able to choose (you, actually) to determine the brightness of a scene. One of them works very well in a majority of simple cases, while the two others are often limited to light situations that are more difficult to manage by your sensor.
Be careful not to confuse everything: these are not the metering modes that will solve the problems of under or over-exposure a photo. It is the metering of your sensor that will be improved and better adapted to the scene you have in front of you. The exposure metering is therefore there to indicate on which areas of the image the metering should be prioritized. Let’s see together in details the three classical exposure metering that are generally found on all DSLR cameras, mirrorless as well and more rarely some bridge/compact cameras.
This is the basic exposure metering found by default on all digital cameras. It can be found under several names: matrix metering (Nikon), multi-zone metering (Pentax & Sony), multi metering (Fujifilm), multiple metering (Panasonic), evaluative metering (Canon) or digital ZESP metering (Olympus). Whatever the name actually is…
Generally speaking, it is the exposure metering we recommend when starting out in photography, time to familiarize yourself with all the other important notions, especially that of exposure (ISO, aperture, shutter speed). The principle is simple for this metering, the sensor determines the brightness of the scene over the entire image. The camera will therefore in this mode determine the general “right exposure” of the scene so as not to favor dark/black areas and light/white areas. By simplifying, it tries to do its best by analyzing the different brightness’s of your scene.
Usually, we say that this type of metering works in 90% of the cases and I must admit that it is the type of metering I use most often. In very special cases of light, I can switch to the other two modes.
The only drawback of this exposure metering is that some cameras combine auto focus lock and exposure metering. This can therefore in some cases mislead the sensor cell even if in practice, I have never found it too much of a problem …
The photo above shows you an example of a shot with this type of exposure. I deliberately chose a delicate situation, a subject (a small braided tree that I brought back from Madagascar) against the light (hard light in the background). As you can see, the sensor tried the best it can not to “burn” the light areas of the image (sky), but also not to make the already dark areas even darker. It tries to find a good compromise for this backlit scene.
But sometimes, it does happen that this basic setting doesn’t correctly measure the exposure of the scene. A sensor being limited in dynamics, it can’t well expose the high and low lights at the same time in very contrasted situations; so, it will underexpose when the scene has a lot of high lights (like here with the sky) or overexpose when it has conversely a lot of low lights. This is where the other types of metering come into play.
In line with the matrix metering, there is the center-weighted metering (Nikon, Sony, Olympus). It is sometimes found under other names at other brands. This metering works slightly differently since it will essentially prioritize the areas close to the center of the image. It is globally an intermediate measure between the matrix metering and the spot metering (which we’ll see afterwards).
It is a mode that I personally use very little. I often choose either the matrix or the spot metering. Here is below the same picture, taken with this exposure metering.
As you can see, the result is even darker than with the matrix metering. This is mainly due to the fact that much of the center is occupied by the sky, the sea, and the tops of trees that are well lit. By lowering the framing to place the horizon on the top third line, the sky would have been less present, and then the exposure metering would have been better.
The last metering that can be useful in some specific situations is the Spot metering. For this one, the camera will simply base its light measurement on a very small portion of the image (less than 5%). The idea is to correctly expose the subject, without taking into account the rest of the image.
If the rest of your image is much darker or lighter than the subject, using this type of metering may over/under-expose the areas very strongly, leading to areas being “burned” (entirely white) or entirely black, depending on whether the subject is very dark in the first case or very light in the second. At the time of film photography, the photometric cell measuring the light was not integrated into the body, so it had to be either positioned near the camera to measure the overall light emitted by the scene (matrix metering) or positioned near the subject to directly measure the light that illuminated it (spot metering).
The picture below shows the same scene and subject again. Focus has been made in the center and on the subject. As you can see, the subject is globally well exposed but the sky in the background is entirely white, which is frankly not ideal either. However, the subject is better exposed than with matrix metering.
I’ll add nevertheless a precision for this spot metering. This type of metering is different according to bodies and brands. At Canon for example, the metering is based on the central AF points which, depending on the composition of the scene you want to do, can become a problem.
This is a small aside (for Canon) but just consider the following. You want to use the spot metering for a sunset, for example, by asking the camera to base its exposure on the clouds and not on the whole scene. If you use the central focus point and then move your camera to compose correctly, the camera will not save your brightness and will redo the exposure metering after your manipulation. So, the trick is to use the * key on your body (it exists at Nikon under the term AE-L or AF-L). This is simply called exposure memorization.
You can reproduce the same manipulation as before with this button activated, which allows the camera to memorize the exposure you did with the central focus point.
In any case, keep in mind that the spot metering is very useful when you want to choose precisely the brightness of a part of a scene.
This is what you should remember about exposure metering in photography. Nothing very complicated, but it can help you in some delicate situations.
Last point quickly (because I decided not to make a separate article about it). There is another possibility to ask your camera to change the exposure metering, without changing the metering mode. This is called exposure compensation. It’s a barbaric word, but it’s basically pretty simple. It is a technique mainly used in aperture priority mode (AV/A) and shutter speed (Tv/S), and not in manual mode (because you can choose whatever you want as settings…).
The principle is simple, thanks to this trick, you will be able to “force” the settings of your camera in terms of exposure. In some cases, the camera won’t be able to correctly measure the exposure of a scene. This is often the case in extremes, like very bright/white areas (snow photography) or dark areas (night, darkness).
I let you check your camera’s manual to know how to apply exposure compensation to a photo, but it’s a matter of moving the cursor you see on your screen between -2/0/+2. The interest is to voluntarily over/under-expose a scene compared to what your camera has measured by default. Pushed to its extreme, you can give a nice special atmosphere (low-key or high-key).
That’s it, I’m coming to the end of this article on metering exposure in photography. I hope I have made it sufficiently clear and taught you a lot, eh? If you want more information or clarification on the subject, please don’t hesitate to leave me a comment at the bottom of the article.
See you soon,