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How to Learn Your Camera’s Light Meter and Master Manual Mode

Most cameras have a few different shooting modes such as Automatic, Aperture Priority (A or Av), Shutter Priority (S or Tv), and Program. It’s not uncommon for people to take a majority of their photos in Automatic mode since it generally does a good job of getting decent results, though more advanced photographers will often use Aperture or Shutter Priority. Shooting in Manual, however, might seem intimidating and highly complex but once you understand a few basics it starts to make a lot more sense. Certainly you should have a working understanding of the three components of the exposure triangle: shutter, aperture, and ISO.

But in order to get the most out of your camera you will need to know how to use a simple, but incredibly powerful, tool that functions as the glue that binds everything together: the light meter.

purple-flowers

Nestled quietly at the bottom of your camera’s viewfinder or Live View display is a small block of lines or bullets accompanied by a few numbers. You might also have noticed a little triangle moving back and forth, or some vertical hash marks appearing and disappearing from time to time, in a fashion that seems nonsensical or completely random. If these numbers and symbols make no sense at all, don’t worry, you are not alone. It can be a bit confusing to understand the light meter at first. But once you get the fundamentals you will probably find yourself growing much more confident in understanding how photography works. Maybe you’ll even venture out of Automatic and into Manual for the sheer amount of control you are able to have over your photos.

Before I get into the nitty gritty of the light meter itself, I want you to take a look at it in relation to the other data shown in your camera’s viewfinder. Note that this diagram is highly simplified and your viewfinder might look slightly different, or include other information, but all cameras (except some point-and-shoots) include the elements shown here.

light-meter-master

In this example the camera’s shutter is set at 1/90 of a second, the lens aperture is f/4.8, and the ISO is 400. The light meter is a readout that shows whether these values are going to result in a photo that is properly exposed – that is, a photo that is neither too light or too dark. The small triangle hovering over the zero in the light meter shows that the exposure is correct, and when the shutter button is pressed the picture will look fine.  But, I’ll show you a few pictures to see what happens as the camera’s exposure settings are changed. If you want to try this yourself you will need to have your camera in Manual mode, and I would recommend reading the rest of this article with your camera at your side so you can do a bit of experimenting on your own.

For my first shot, I’ll show you a photo that is underexposed and then illustrate how the camera settings can be adjusted to get the proper exposure. The values shown on these images are exactly what I used in my camera to get these shots, and nothing has been edited or retouched in Photoshop.

landscape-under

Here you can see that the shutter speed is 1/1000 of a second, the aperture of the lens is f/4, and the ISO is 200. The camera’s viewfinder displays this information along with the light meter, and note how the triangle has moved all the way over to -3 EV. (EV stands for Exposure Value, and technically this image is underexposed by three stops. Don’t worry about the technical jargon though! For now just follow along with the examples to see what happens when the exposure values are altered.

To get a properly exposed photo you are essentially trying to re-create what your eye already sees, but right now the light meter tells us that the photo will be way too dark. And indeed, the resulting photo turned out just how the light meter predicted: it’s so dark it looks like it was taken at night instead of mid-afternoon.

So what can be done to fix this? By adjusting the aperture, shutter, or ISO you can change the exposure settings with the goal of getting that little triangle to hover above the zero. Watch what happens when I change the shutter speed but I leave the aperture and ISO fixed at their present values:

landscape-over

By altering the shutter speed from 1/1000 of a second to 1/15 of a second, the photo is now too bright – exactly as the light meter said it would. It is overexposed by three stops, and the image is virtually unusable. Because the viewfinder itself does not change as the aperture, shutter, and ISO are adjusted, you have to rely on your light meter to tell you how bright or dark the image will be. And sure enough, the triangle is hovering above the +3, which tells us the photo will be too bright. Here is what a properly exposed photo looks like.

landscape-correct

Finally, a good picture! By adjusting the shutter speed to 1/125 of a second, I was able to get the triangle to hover above the zero, which means the photo would be properly exposed. Note that there is no one correct way to do this, and a proper exposure could have also been obtained by changing the aperture or ISO instead of the shutter speed, or a combination of all three. For instance, I could have left the shutter at 1/1000 and increased the ISO to get the same result.

Why bother with all this?

At this point you might be wondering why you would want to go to all this trouble when you can put your camera in Automatic mode and it will just take care of everything. The answer lies in the fact that you, not your camera, know exactly what kind of photo you want to take. Your camera does not know whether you are shooting landscapes, portraits, sports, starry nights, kids, pets, or anything else. All it sees is how much light is coming in, and it tries to adjust the shutter, aperture, and ISO to get that triangle to hover above the zero. But if you know how to control those values yourself, you can open up vast new areas of photographic creativity that Automatic mode can never do for you.

As another example, here is a picture of some berries, but again notice how it is underexposed by three stops.

berries-underesposed

There are several settings I could adjust in order to fix this, or I could just put the camera in Automatic mode. The problem with Automatic in this case is the camera does not know that I am looking at berries. It just sees light, and would attempt to adjust the shutter, aperture, and ISO to get a proper exposure even though it might not end up with the exact type of picture I want to take.

Because I shot in manual using the light meter as my guide I was able to get precisely the shot I was looking for. I knew that I wanted a shallow depth of field, which meant I should use a large aperture of f/2.8. I knew that an aperture of f/1.8 would be too wide for my taste, and a smaller value like f/4 or f/8 would not give me the nice blurry background I was hoping for. By leaving the aperture at f/2.8 and changing the shutter speed I got a properly exposed photo with a nice smooth background as you can see here:

berries-correct

But what if I had changed the other values instead? Look what happened when I left the aperture and shutter at their original values from the underexposed photo (f/2.8 and 1/1000), and raised the ISO instead:

berries-correct-high-ISO

The end result is almost the same: a properly exposed photo (just like our light meter told us it would be, with the triangle hovering above the zero), but this image has much more noise and grain than the previous one. Notice how the tree in the background just behind the berries looks speckled and grainy instead of silky smooth, which is what usually happens at high ISO values. Thus, raising the ISO might not be the best way to get the image I want even though the photo itself is properly exposed.

So what about changing the aperture instead?

berries-correct-small-aperture

Once again the result is a photo that is properly exposed, but the depth of field is much wider – see how the background is not quite as smooth and blurry as before? Also, because the aperture was smaller I had to leave the shutter open longer at 1/90 of a second and even raise the ISO a bit in order to maintain a proper exposure.

Get the exact shot you envision

Shooting in manual and using the light meter as your guide is a good way to ensure that the image you see in your mind is exactly what you end up with when you click the shutter. If you are shooting fast-moving subjects like cars or sports, you would want to start with a fast shutter speed and adjust the other settings until you get that little triangle to hover above the zero. If you are taking portraits and want a shallow depth of field with nice blurry backgrounds, keep the aperture wide and change the shutter and ISO until the exposure is correct. It’s all about giving control back to you, the photographer, instead of letting your camera make the creative decisions for you.

construction-lights

Shooting in manual was the only way to capture this photo. By reading the light meter while carefully adjusting my exposure settings I got precisely the shot I was aiming for. Camera settings: f/16, 1/3 second, ISO 800

Understanding the basics of the light meter is really just scratching the surface, though. Additional settings like your camera’s metering mode and the Exposure Lock function are even more tools you can use to take control over your photography and unlock your true artistic potential. Using manual mode and reading the light meter might seem like a complicated way to take photos, but remember that you know better than your camera what kind of picture you want to take. Once you know how to read your light meter and adjust your camera’s settings accordingly, you can open up a whole new world of creativity that has been right in front of you just waiting to be discovered.

Practice time

So now it’s your turn: grab your camera, put it in Manual mode, and hold the viewfinder up to your eye. Now start changing the aperture, shutter, and ISO values and watch what happens to the light meter. Is your image going to be overexposed? Lower the ISO, raise your shutter, tighten the aperture, or try a combination of all three. Is your image going to be underexposed? Do the exact opposite. The more practice you get, the easier it will be and soon you will feel much more comfortable shooting in a mode that might have seemed hopelessly confusing before.

Do you shoot in manual? If so, how did you get yourself off Automatic mode? Or do you actually prefer Automatic? Share your thoughts and experiences in the comments below.

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Simon Ringsmuth
Simon Ringsmuth

is an educational technology specialist at Oklahoma State University and enjoys sharing his enthusiasm for photography on his website and podcast at Weekly Fifty. He and his brother host a monthly podcast called Camera Dads where they discuss photography and fatherhood, and Simon also posts regularly to Instagram where you can follow him as @sringsmuth.