How to Use Your Camera’s Exposure Meter

You’ve mastered the basics of working in your camera’s Manual mode by using shutter speed, ISO and aperture to control your exposure. But how can you tell if your image is going to be properly exposed, other than by trial and error or guessing what settings you need?

In this article, we’re going to look at how using your camera’s built in light meter will take all the guesswork out of getting correct exposure. It’s a simple yet powerful tool that is often overlooked. As you gain in experience of using manual mode, you will probably find you use your light meter much less. For beginners, it’s invaluable, and if you’re shooting film, it’s essential!

Where is My Light Meter?

You may be wondering where this amazing tool is located on your camera. Look into your viewfinder, and right at the bottom you’ll see a long, rectangular display filled with lines, numbers and dots, or some variation of these depending on what brand of camera you’re using.

This display also shows what shutter speed you’re using, your aperture and your ISO. There is usually a red or green inverted triangle or large dot along the top line of the numbers and dots. This triangle or dot is what tells you whether your photo will be properly exposed when you press the shutter.

How Does it Work?

In order to gain proper exposure, the aim is to get the triangle or dot to hover above the 0 in the middle of your light meter. The 0 symbol stands for correct exposure. All the numbers to the left of this 0 show if you’re underexposed, and all the numbers to the right show if you’re overexposed. To get the triangle or dot above the 0 symbol, you need to adjust either shutter speed, aperture, ISO or a combination of all three.

Pick your camera up, put it in manual mode, and look through the viewfinder. What does your display tell you? If the triangle is on the left side of the 0 symbol, this means you’re underexposed, and the number it’s hovering above tells you by how many stops. If it’s on the right hand side of the 0, it means you’re overexposed, and again, the number it’s above tells you by how many stops.

The Meter Tells Me I’m Underexposing

Now try adjusting your shutter speed. If you’re underexposing, lower your shutter speed until the triangle or dot is above 0. It may go down to a very low shutter speed if you’re in a darker area, and this would mean you couldn’t take a hand-held shot without it being blurred.

What do you do in that scenario? Lower your shutter speed to a point where you know you can hand-hold it without camera shake blurring the photo, (for me, that’s around 1/80^th second) and adjust your aperture to a lower f-number. If you want to shoot at the same aperture that you’re already on, you’ll have to adjust your ISO upwards instead. Experiment until you get the triangle or dot above the 0 symbol on the light meter.

You could also use a tripod if you want to shoot at lower shutter speeds without raising your ISO or adjusting your aperture to let more light in.

The Meter Tells Me I’m Overexposing

If the meter is hovering to the right of 0, and you’re already on the lowest ISO number you have, you can only change the shutter speed or increase your f-number. Dealing with overexposure is often easier than underexposure, as your camera’s shutter speed will go very high indeed, meaning you don’t have to change your aperture if you don’t want to, and you can hand-hold at higher shutter speeds without worrying about camera shake.

Why Bother Using The Light Meter?

Sure, you could just put your camera into Program or Automatic mode, and it’ll work out the correct exposure without you having to do anything, but you’ll lose the ability to get the shot you want. The camera will decide aperture, shutter speed and ISO, not you.

The resulting image might have too much noise in it from the camera raising the ISO, or it may take the shot with a wide or shallow depth of field that you may not like. It may drop the shutter speed to point where your image will come out blurred unless the camera is on a tripod. It takes the creative choice away from you.

It may seem complicated to master at first, but it really is as simple as seeing which side of the 0 symbol the meter is on, and adjusting your settings until you hit that 0 for correct exposure.

Is The Light Meter Always Right?

No. There are certain circumstances when the light meter gets confused and tells you that you have correct exposure when you don’t. Luckily, there’s only two scenarios where this happens, and that’s shooting a scene that’s predominantly white or predominantly black.

Correctly Exposing a White Subject

Think of shooting a beautiful, white snowy scene in daylight. Your camera tells you that you have correct exposure, and you click away happily. Imagine your frustration when that bright, white snow comes out on your camera display as dull gray. It’s underexposed, even when your meter is telling you it’s not.

Why? The camera meter gets confused because all that bright white in front of the lens makes it think that you’re overexposing when you’re not. If you shoot snow in bright daylight, always overexpose your images by 1.5 to 2 stops. Then the snow will be that dazzling white you see in front of you. Adjust your settings until your light meter tells you you’re overexposing by the triangle hovering over the +1.5 to +2 on the right-hand side of your meter.

Correctly Exposing a Dark Subject

If you want to shoot a predominantly black or very dark subject, you need to do the opposite. Again, the dark colors confuse the light meter into thinking it’s underexposing when it’s not. If you shoot at what it says are the correct settings, you’ll get a horrible, washed out dark grey instead of black. The solution to this is to set your camera to underexpose by 1 stop. Adjust settings until the triangle or dot is above the -1 symbol to the left of 0 on your light meter. Now your images will come out with true blacks.

Are There Any Other Colors to Watch Out For?

If you want to take an image of something that’s mostly red, crimson, deep purple or deep blue, it’s often best to treat them like black, and underexpose by -1 stop.

If you are shooting something predominantly bright yellow, light pink, light orange or peach, treat them as white and overexpose by around +1 stop.

Final Thoughts

Using your light meter is simple once you understand it, and will help you get the creative images you want. Not everyone likes using them though, and some people prefer to underexpose all their images slightly, or overexpose slightly. What are your preferences? Do you find light meters indispensable, or do you prefer to trust your own judgement?

In the next article, we’re going to look at your camera’s metering modes: spot, center weighted and matrix, and what the differences between them are.