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Perfect Exposure Every Time: A Guide to Metering in the Viewfinder

This post is part of a series called Ready, Set, Exposure.
How to Use Your Smartphone as a Light Meter
A Simple Solution to White Balance and Exposure: The 18% Gray Card

You'd be surprised how much information is available through your camera's viewfinder. In today's tutorial, we're looking again at one of the most important elements of photography - exposure - and how you can expose a perfect photo using just the information shown in your camera viewfinder!

Republished Tutorial

Every few weeks, we revisit some of our reader's favorite posts from throughout the history of the site. This tutorial was first published in June of 2010.

Perfect Exposure

When I first began learning photography, mastering exposure settings seemed to be one of the trickiest things to grasp. To get a decent exposure, my workflow usually consisted of snapping a picture, viewing the result, fiddling with the settings nearly at random, and then trying again only to repeat the cycle over and over while hoping to stumble onto a decent result. As a beginner, this can be immensely frustrating. It wasn't until I had a strong grasp of how the exposure settings affected the end result that I really began taking nice photographs fairly easily.

Armed with this knowledge, I could at least figure out how to interpret my test picture and adjust the camera settings accordingly a few times until I was happy with the result. Then one day someone showed me a simple trick that changed everything. Since I lacked any sort of formal training I had completely missed the fact that my camera would actually tell me how far off my exposure was and guide me to the "sweet spot" without ever pulling my eye from the viewfinder!

This brief tutorial is for complete beginners who, like me when I first started, have no clue how to make your fancy camera take a picture that isn't either too dark or too bright. As such, I'll keep everything really basic and as non-technical as possible. It's also important to note that while the principals outlined here apply to all digital SLRs, the functionality discussed below applies specifically to Canons and may require some interpretation to be applied to cameras from other manufacturers.

Exposure: The Basic Idea

Our recent Beginner's Guide to Exposure explained in great detail everything you need to know about exposure. For those of you who haven't read this, I'll very briefly explain what you need to know for the purposes of this tutorial.

Exposure loosely refers to the amount of light that is let into the sensor on your camera. The more light you let in, the brighter the resulting picture. Conversely, the less light you let in, the darker the picture.

How much light is let in is a function of your shutter speed and aperture. The shutter speed is commonly expressed in fractions of a second. For example, if you see a setting that says 1/125, 1/50, etc. this is your shutter speed. Shutter speed is exactly what it sounds like: the amount of time the shutter opens to let light in.

Since the number is a fraction, the smaller the denominator (the number on the bottom), the longer the exposure. For example, 1/200th of a second is a much shorter amount of time than 1/10th of a second. Consequently, a shutter speed of 1/200th of a second will let in much less light and produce a much darker image than a shutter speed of 1/10th of a second. Also note that the longer the exposure, the blurrier any action in the photo will become.

lighting chart

The aperture setting controls how much light is let in by varying the size of the opening through which the light must enter and is expressed in terms of focal length (f/x). The smaller the number associated with the denominator of the focal length, the greater the size of the hole, which means more light entering the camera and consequently a brighter picture.

lighting chart

Also remember that the lower the denominator is on the focal length, the shallower the depth of field. This means that the area of the picture that is in focus is fairly large at f/11 and higher, and fairly small at f/3 and lower.

Don't Forget ISO!

Your ISO setting will also affect the brightness of the picture in conjunction with the quality. Without getting into the complexities of your camera's electronic sensor, suffice to say that the higher the ISO, the brighter the resulting picture. Unfortunately, as ISO increases so does color noise, which really brings down the quality of the photo.

lighting chart

Metering in the Camera

Hopefully that's all pretty straightforward. If you're confused by all the explanation, the three images above tell you everything you need to know. If you need your image to be brighter, decrease the denominator in both the aperture and shutter speed and increase the ISO. If you need your image to be darker, increase the denominator in both the aperture and shutter speed and decrease the ISO (you'll quickly learn to feel out all three together).

As you know, when you're shooting in full auto, your camera attempts to make all these judgement calls for you. However, as a photographer, you should be comfortable shooting on full manual as you'll have much more control over the results when you can fine tune the settings.

The nice thing about all this is that even in manual mode, your camera is giving you hints as to what it thinks your exposure should be. Try pointing your camera at a subject and pressing the shoot button half way. You should hear a beep from the autofocus as the camera attempts to interpret what you want to focus on.

This beep signifies more than the autofocus however, as much more is going on automatically behind the scenes. To see what I mean, look into your viewfinder. You should see lots of numbers and settings that will vary from camera to camera, but they should at least resemble the simplified graphic below.


As you can see, all of the settings we discussed above are represented right here in the viewfinder. When you perform that half-press on the shoot button and hear the beep, these indicators will light up and show you the settings you've selected as well as how the camera interprets the available light.


Here the camera is telling us that we've set our shutter speed to 1/125, our focal length to 4.0 and our ISO to 200. The real magic however is happening with the Exposure Level Indicator (ELI). This is telling us that we aren't letting enough light into the camera. We know this because the little light on the bottom is lit up to the left of center. If it were lit up to the right of center, we would know that we are letting too much light in. The goal then is to get this little guy lined up right down the middle.


Theoretically, this should help you achieve a picture that is neither too bright, nor too dark. Admittedly, some exposure bias is sometimes necessary but this method should work just fine a great deal of the time. To put this into practice, let's imagine a shooting scenario.

Getting the Perfect Shot

Let's say you're indoors shooting a birthday party during the day. As is often the case, the light is decent, but not great. Using the information above, you know that since there's not a lot of light available, you'll probably want to bump your ISO up to 800. Sure you'd love to shoot down at 100 but it simply won't be possible given the conditions.

You also know that the poor lighting means you'll want your aperture wide open. Let's say your lens will only go down to f/4, so that's where you'll set the aperture. You're fine with the shallower depth of field because it produces that nice blurry background and crisp subject that you see often in professional photography.

Since you're shooting moving people, you want your shutter speed to be fast enough to have crisp photos devoid of blur where someone was moving. Consequently, you'll start with a shutter speed of 1/200.

Next, you look into your viewfinder, focus on your subject, and see the following:


You can instantly tell, even before you take a single picture, that the image is going to be too dark. Your aperture is as open as you can get it and you don't want to sacrifice any more quality, so your only option is to decrease the speed of your shutter to allow more light in.

The brilliant part is that you can accomplish this without even removing your eye from the viewfinder. With the camera up to your eye, there should be a little wheel next to your right index finger. Turn this wheel to adjust your shutter speed. Oddly enough, turning the wheel left will make the ELI go right and turing the wheel right will make it go left (it might be the opposite on a Nikon). You can actually change all of the settings above without leaving the viewfinder, consult your camera's manual for how to do this on your specific model.

So to fix the problem shown in the picture above, simply move the wheel left until the indicator is centered.


A shutter speed of 1/100 should be quick enough to shoot handheld without too much blurring. Keep in mind that if you go any longer, you'll want to shoot stiller subjects and/or implement a tripod to keep things steady.

If you're shooting handheld and centering the ELI means dropping your shutter speed too low (say 1/50), try upping your ISO or lowering your focal length (if your lens will allow). Note that if you're using a flash, you can shoot at much slower shutter speeds as the flash captures the motion in place.

Using AV and Auto Modes

If you're really lost on where to set all of your settings to start things off, try switching to auto mode and metering there. This should get you in the right neighborhood to start playing with your own settings in manual mode.

Sometimes you'll find yourself shooting a scene that is changing so quickly that using manual mode becomes cumbersome and annoying. I recently shot an outside hockey game at night where this was the case. The lighting in different areas of the rink varied dramatically, the players were of course constantly moving and I was experimenting with different zoom levels. Consequently, shooting in full manual would've required a lot more settings adjustments and a lot less shooting than I would've liked.

In these circumstances, it's a good idea to shoot in AV. This mode allows you to set your own ISO and aperture so you have control over your depth of field and color noise. However, it automatically takes care of your shutter speed for you. If you look into the viewfinder in this mode, you'll see that you camera dynamically adjusts the settings so that the ELI is in the center no matter where you're shooting.

When shooting in AV, you still have to keep an eye on your shutter speed to make sure your camera isn't putting it too slow. Again, any time it starts dipping too much below 1/100, try adjusting your other settings to allow more light in. Even if your pictures are looking decent on the small screen, you'll be disappointed to see how blurry they are when you import them into your computer and view them at full size.

Try to resist shooting in either AV or auto mode when you don't have to. The more practice you get in on full manual, the more you'll become comfortable with every setting on your camera. This will enable you to confidently approach setting your own exposure in nearly every situation and will help you become a much better photographer.


To sum up, if your pictures are too bright, try increasing your shutter speed, upping your aperture (higher number, smaller hole), and/or reducing your ISO. Conversely, if your pictures are too dark, decrease your shutter speed, reduce the aperture, and/or increase your ISO.

Watch the Exposure Level Indicator in your camera's viewfinder closely and try to adjust your settings so that it lines up perfectly in the center. If for some reason this produces a picture that is still too dark or too bright, apply exposure bias accordingly.

Finally, if you have trouble shooting in manual, start off in auto to get a feel for the proper settings or switch to AV so the camera will automatically control only your shutter speed while you take care of the rest.

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