OK. You're just starting to get the hang of this whole picture-taking thing. You've taken some remarkable photos that you've posted on social media, and people are going gaga over your pictures. You think, "I got this! This photography is a piece of cake!" You take your kiddo to the park and are loving the beautiful light that is making your kid's hair glow! You grab your trusty camera, snap a few shots, look at your screen, and are disappointed to see that your poor kid's face is totally underexposed. What gives???
While this topic of metering might cause a switch in your brain to automatically shut off while your feet start running you in the other direction, I'm telling you, understanding how your camera reads light and getting away from the fully-auto green mode will make a world of difference in the quality of your images. Stay with me. You'll be glad you did.
Typically, when you are taking a portrait, you want your subject to be properly exposed--not too dark and not too bright, right? We learned in my article about the exposure triangle that if your images are too dark, you need to let in more light, and if your images are too light, you need to let in less light. And while your meter will do its best to choose a proper exposure, it won't always get it right. Understanding how your camera meters for a scene will help you control your exposure so you get your subject exposed the way you want. Sounds pretty great, huh?
So, what is that meter in your camera doing? Your meter's only job in life is to take the area that it has been told to use, mix all the tones together, and come up with an exposure that will make that area average or middle gray. Your meter usually doesn't care about color, it is only concerned with how bright or dark the tones are. Middle gray is basically the tone that is halfway between white and black.
When I was learning to understand metering, I bought a middle gray, or 18% gray card to help me understand what my meter was designed to do. I used it to set my meter until I started understanding exposure better and no longer needed to depend on it. Your camera's meter doesn't know what subjects are black or what is white, just middle gray, so it's up to you to understand what your meter wants to do and know when you need to make adjustments.
So, let's say that I took my middle gray card, filled the entire frame with just the card, and set my meter to zero setting (indicating proper exposure). I would get an image where my middle gray card would look exactly the way it does in real life. It would still be middle gray.
Now, let's say I took a white card, filled the entire frame so that all I could see was white, and again, set my meter to zero. What would I get? Would I get a white image? Nope. The meter's job is to make the exposure middle gray regardless of what you actually see in real life. So, what do I get when I meter off of a white card? The meter sees the white as too bright, and therefore UNDERexposes, so that I get middle gray. Have you noticed that when you shoot your kids playing in the snow, your kids look dark and the snow looks gray? That's because all that white is too bright, and your meter wants to make it middle gray. Ever noticed how dark your kids look in pictures when they have a brighter light source behind them? All that bright light makes your meter want to underexpose.
How about if I filled my entire frame with a piece of black paper, set my meter to zero, and took a shot? If you're thinking that you won't get a black image, you're right! The meter sees all that black, and thinks, "oh dearie me, this is dark. I better OVERexpose so I can make this brighter and turn it to middle gray." Ever photograph your kids in a dark woodsy area and notice that your photo looks too bright? Your meter sees that darkness and wants to brighten it up. This happened to me early on in my photography journey. I shot a series of images at a Christmas tree farm and did not understand why all my pictures were so bright. Those dark trees surrounding my kids tricked my meter into thinking it needed to overexpose. Stupid trees. Humph.
So, while the meter will do its best to give you a good exposure, it won't always get it right. It's up to you to know what your meter wants to do and know when you will need to intentionally under or overexpose so you get the exposure that YOU want. If you are metering off of something that is BRIGHTER than middle gray, you will need to OVERexpose (let in more light) since your meter wants you to underexpose. If you are metering off of something that is DARKER than middle gray, you will need to UNDERexpose (let in less light) since your meter wants to overexpose. It's a little reverse psychology for your meter, if you will.
But here's the thing... it's not like you're metering off of sheets of paper, now are you? You're looking at a scene and having to figure out your exposure. You certainly aren't filling your frame with one tone and figuring out your exposure. This is where knowing your metering modes and choosing the appropriate one for the situation can be helpful. This doesn't mean that you need to use ALL the metering modes. Many professional photographers only use one or two, but in this article, I intend to at least familiarize you with all of the choices, so you can make a decision on which ones you want to use and why.
Canon EOS cameras have four different metering modes:
Evaluative metering: This is the default setting in your Canon EOS camera and for good reason, as it is quite sophisticated. If you are using the auto green mode, you are always using evaluative metering. You cannot change to a different metering mode until you turn your dial away from the green mode and work your way into the Creative Zone exposure modes of Program, Av, Tv, or Manual. With evaluative metering, nearly the entire picture area is analyzed, and corrections are made automatically if unusual lighting is detected. It actually even "knows" which Autofocus points were used, assumes this is the most important part of the image, analyzes the surrounding area, and determines a "correct" exposure. Because the active Autofocus point is used to help determine the exposure, focusing on a different subject in the same scene may give you a different exposure. Keep in mind, however, that evaluative metering is assuming that it is analyzing normal subjects with an average brightness.
Evaluative metering works great when your subject and background are evenly lit by the same light. It's perfect for when you're shooting your subject in full sun where the sun is in front of your subject or when your subject is in soft, even light. Leave your meter at zero, and your subject will be perfectly exposed. Sure, there will be times you’ll need to compensate and deliberately lighten or darken a shot with Evaluative metering — but especially with automatic exposure, it’s a good starting point.
Here, the sun is illuminating my crazy boy as well as the grass and sky. I used evaluative metering with the meter set to zero, and got this shot.
In this shot to the right, my daughter and her surroundings are both softly lit in an open area where the sun has just recently hidden itself behind a hill. The light is even throughout the frame. The camera will put more priority on my Autofocus point (which is pointing at my daughter) and the areas around the Autofocus point, and will determine a correct exposure.
Center weighted metering: Averages the exposure for the entire metering area, but concentrates on the center of the scene, since the most important areas of an image are usually in the center. Unlike Evaluative metering, it does not compare brightness readings from different parts of the scene nor does it use Autofocus points to determine where the subject is in the frame; it simply reads overall brightness. Center weighted metering has the nice advantage of being predictable. If you understand that your meter is concentrating on the center of your scene, you can begin to understand when you would want to use exposure compensation (discussed below) to overexpose or underexpose your image.
Spot metering: With spot metering, your camera reads exposure from a single exposure zone in the center of the frame (only about 3% of the total picture area.) You are essentially telling your camera "this is the area I want to use to determine exposure."
I use spot metering whenever my subject is surrounded by either a significantly brighter or darker scene, and I always use manual mode when using spot metering. As a portrait photographer, I often want my subject to be properly exposed (not too dark and not too light). I simply aim the center of my camera at my subject, typically a cheek, and set my meter accordingly. For Caucasian skin, this usually means setting my meter to be overexposed 2/3 to a full stop, since Caucasian skin is a bit brighter than the average mid-tone of middle gray. If I'm metering off of someone with a darker complexion, I may leave my meter at zero or even underexpose, depending on the tone of their skin. Once my meter is set, I can recompose and take my pictures, knowing that my subject will be properly exposed.
So, if you set your meter to zero with that little spot pointing at something that is an average tone, you will get a well exposed image because that's what your meter is supposed to do: make an average exposure. If you point that spot at an area that is brighter than middle gray and set your meter to zero, your camera will UNDERexpose in order to get that area to be middle gray because it wants everything to be that average, middle gray tone.
Partial metering: Partial metering is like spot metering, but it covers a larger area in the center of your frame (about 10% of the total picture). This can be useful for controlled metering off faces when shooting a portrait, for example.
If you are just starting out and are feeling overwhelmed by these choices, I would try using either evaluative or center weighted metering. Evaluative metering is the default system on your camera for good reason. That technology is pretty dang smart, and as long as you understand and learn to compensate for the fact that it is assuming your subjects are normal brightness, you'll love it.
So, you now have a basic understanding of the different metering modes, bravely switched your dial away from automatic green mode and are venturing into P, Av, Tv, or M. What the heck does this even mean???
A quick overview of Program, Av, Tv, and Manual
Program mode (P) allows you to choose your ISO and then your camera will select both your aperture and your shutter speed. It is still fairly automatic, like the auto green mode. I personally have never used Program mode, but recognize that it can be a great first step from getting away from auto green mode. The benefit of Program mode is that unlike being in auto green mode, you now have access to more features. For a great description of these features, check out Rudy Winston's article right here. The disadvantage of Program mode is that you do not have good control over what your aperture and shutter speed will be, which limits your ability to have creative control over your images. If you've read this far, it tells me you want to have a better understanding of your camera and have greater control over your images. I'd suggest skipping P mode.
Aperture Priority mode (Av) allows you to select your aperture and ISO, and your shutter speed is then automatically determined. When you are most concerned about controlling your depth of field (how much of your photo will be in focus and how much will be blurry), Av is a great choice. Once your aperture is set, it will stay put. If you choose an aperture of f/2.8, for example, and note that your shutter speed is too slow for your liking, you just need to increase your ISO, which will then allow your shutter speed to go higher. This bears repeating: if your shutter speed is too low, which will cause motion blur, increase your ISO to allow for a faster shutter speed to freeze action as well as camera shake. I love Av mode and use it often. It's great when you are moving in and out of different lighting situations and want your aperture to stay consistent. I use it with Evaluative or Center Weighted Metering. I never use Spot Metering with Av mode, as exposure would change drastically as the scene changed.
Tv mode (Shutter Priority) allows you to select your shutter speed and ISO, and your camera then sets the aperture. When controlling your shutter speed is the biggest priority, Tv mode is your friend. If you want to ensure that your shutter speed is fast enough to freeze your fast moving toddler's actions, then try setting your shutter speed to at least 1/500s. If you notice that your f-stop is as low as it can go and is blinking on your viewfinder display, that means that you're in danger of underexposing your image and you’ll need to increase your ISO (or, select a slower shutter speed).
In Manual mode (M), you control all three corners of the exposure triangle: ISO, aperture, and shutter speed. This allows you the greatest control over your exposure as you are responsible for what each setting is. Nothing is automatic. Your camera's exposure scale in the viewfinder will provide information as to whether it thinks your image is underexposed (to the left of zero) or overexposed (to the right of zero). You may want to jump right into playing with manual mode, or you might want to take some smaller baby steps, like I did, when you're ready to step away from auto green mode.
One other thing about Manual mode: once you determine and set your exposure manually, it STAYS there, and won’t change on its own if your composition changes, or even if your subject changes (like switching from a person in a light-colored shirt or jacket to another person wearing darker clothes). As long as the actual light falling on your scene hasn’t changed, this can be a good thing!
Note: there is a semi-automatic manual mode in some midrange Canon EOS cameras. You can set your ISO to "auto ISO" and dial in your desired shutter speed and aperture. Your camera will adjust the ISO to make your exposure. This can be useful when there is ever changing light, but keep in mind, your camera will always choose an average exposure. You cannot overexpose or underexpose using this set up, with most EOS models.
In P, Av, and Tv mode, your camera will do its best to make a "correct" exposure, but it won't always do it right. Using exposure compensation is a quick and easy way for you to make your image brighter or darker with the camera still helping you determine part of your exposure triangle.
Let's put this all together:
We're stepping away from auto green zone. We want to take a picture of our cute kid eating snow. We set our metering mode to Evaluative Metering and choose Av mode. We want the trees in the background and people marching around the park to be out of focus and blurry, which means we want a shallow depth of field (a low f/number). Using our 50mm f/1.4 lens, we choose f/1.8. It's a bright day, so we choose an ISO of 100. With our meter set to zero, our camera chooses a shutter speed of 1/2500s for a "correct exposure." If we fire off the shot, this is what it would look like.
The camera did its best to give us a proper exposure, but remember, evaluative metering is programmed to give you an average exposure for an average scene. Snow isn't average...it's bright. So, in a situation like this, your meter will usually underexpose the image in an attempt to get an average exposure. But, never fear! YOU know that if you are shooting where there is a brighter than average scene like with backlighting or snow, you'll have to compensate for this unusual lighting situation. You know your camera will see all that brightness and underexpose, so you use Exposure Compensation to OVERexpose by about 1 1/3 stop (Note: how much you overexpose depends on the exact scene. Sometimes it will be more. Sometimes it will be less.) This essentially brightens your image by decreasing your shutter speed from 1/2500s to 1/1000s. A slower shutter speed means more light, so BAM, you get a nicely exposed image of your son eating snow. Pat yourself on the back, you have a cute kid. And then pat yourself on the back because you just knew your meter well enough to know when you'd need to make adjustments. That's no small feat!
Could I have used a different metering mode? Absolutely! Using Aperture priority (Av) with Center-Weighted would likely have given similar results. With center-weighted metering, the camera concentrates on the center of the image, but still reads most of the entire picture area.
The middle part of the image, in this case, my son and some of the snow, would have been averaged to produce an exposure. And this is about what my exposure would be.
Why is it underexposed? When the meter analyzes a scene, it usually only “sees” the image in black and white.
Then, with Center Weighted metering, the center portion is emphasized. When the center portion of this image is analyzed, the result is a tone that is brighter than middle gray, so the camera will underexpose to get middle gray. In order to get my son and snow properly exposed, and not too dark, I would need to use exposure compensation and overexpose.
What if I was taking a picture of my son where he remained centered in the frame but I chose to compose it so that he was smaller in the frame and there was a lot more snow around him? There would be a greater amount of areas lighter than middle gray in the center area, and I would have to overexpose even further in order to get a good exposure on the snow and my son. Make sense?
While this all seems complicated, it really isn't. The great thing about our cameras is we can fire off a shot, look at our LCD, and get an idea of whether or not we are in the ballpark. We can also use "live view" so we can see what our exposure will look like before we even hit the shutter. SCORE.
Please note: I only went into a more detailed discussion of evaluative and center weighted metering because I think these two metering modes are less complicated than using spot metering for a beginner. I absolutely use spot metering, as do many professional photographers. It allows you supreme control over all areas of the exposure triangle and can be invaluable in tricky lighting conditions.
Just another little note. Your camera is pretty dang sweet, and has a function called "Highlight Alert" that can be enabled or disabled in your menu system. I always have this turned on. When playing back your pictures on the camera’s LCD monitor, if your image has areas that are so bright there is very little detail in it, those parts of the image will blink on and off. You can then make a decision if those areas are important to you. Perhaps you don't care if the background is completely white and bright as long as your subject is properly exposed. You get to decide. I absolutely avoid having my subject too bright. If I take a picture and note that there are "blinkies" on my subject's face, I always lower my exposure.
Backlighting and underexposure
So, let's talk about one of the exposure problems I see the most often: backlit, underexposed, dark subjects. This can happen, as shown above, when there is a lot of snow that "tricks" the meter into thinking it needs to darken the snow. But, this problem of underexposure is not unique to snowy days. If you are shooting your subject where there is brighter light behind them (backlight, window light), it's likely that your meter won't get your exposure right.
Here's an example:
My son took a break from running around to sit down in this lovely area where he was nicely backlit. Okay, okay... perhaps I encouraged him to go sit over there... Regardless, there he is. I snap a picture in Aperture Priority mode (Av) using Evaluative metering. My meter is set to zero. I get an underexposed image of him.
I take a quick peek at my LCD and see that he's looking pretty dark. I use exposure compensation and overexpose a full stop. This means my entire image will be twice as bright as it was with my first shot. Now I get a properly exposed image of my little guy.
My little sweetie. He's ALWAYS so cooperative when I want to take his picture. NEVER makes a funny face. Ever.
Until next time! Have fun practicing!
The CDLC contributors are compensated spokespersons and actual users of the Canon products that they promote.