When you first venture away from auto mode, it might be a hard to wrap your head around the process of taking the correct exposure. Playing around with the “exposure triangle” (aperture, shutter speed, and ISO) seems to be mainly guesswork that leads you to no good places, and after a while, you just want to go back to your safe place - auto mode.

However, understanding how your camera measures light is necessary to take pictures in Manual Mode, or appropriately use Aperture Priority/Shutter Priority modes - and that is the only way to gain complete artistic freedom.

See, most DSLR cameras use a through-the-lens (TTL) system to measure the light in front of it. It does this by measuring the light that passes through the lens and gives you the reading either on your LCD or in your viewfinder. Once you learn to read this meter, you can manually change it to your advantage, and create more interesting shots as a result.

In more advanced cameras you might have the multi-point metering systems. These measure light on a number of different points scattered throughout the scene instead of just one. This allows you to have even more control of your main focus point, and become even more creative with your photographs.

This is why it’s important to take the time and learn light metering on your DSLR because sticking to auto mode will constrict you as an artist.

So let’s get to it! Don’t be worried, it sounds much more complicated than it looks.

The Light Metering Display

When you look through your viewfinder, you may have noticed a strange little scale at the bottom of it. It goes from -3 all the way up to +3, and is divided with small dots in between (sometimes instead of numbers it has little rectangles). When you point your camera at different things, there should be a little triangle dancing along that scale. 

This is your light meter, and for correct exposure, you want that triangle to be at zero value.  

In auto mode, your camera does all the work for you, and every picture you take is automatically near the center of this scale. But once you start using different camera modes, you will have to refer to this scale if you want to easily determine what settings you should be using.

However, in manual mode, it’s a little bit more complicated. When the camera measures the light, it determines the overall value of it and compares it to the settings that you have dialed in. If in respect to your desired settings there is not enough light, the little triangle will move towards the -3, indicating that the picture is underexposed. If you were to fully press your shutter release now, you would end up with a picture that is much too dark, or even completely black.

Learn More:

• Demystified: AF Lock and AE Lock
• How to Fix Common Exposure Problems

Using Light Metering in Manual Mode

Shooting in aperture priority or shutter priority modes might give you an indication of how the light metering behaves, but you don’t start to fully utilize it until you set your camera to manual mode. Now, you are responsible for picking out the settings you want, which gives you full control of your creativity.

Here’s how you can fully utilize your camera’s built-in light meter:

1. Determine what kind of shot you will be taking and which setting is going to be most appropriate. For example, for a fast moving object, you will want a higher shutter speed to capture the motion. But if you are taking portraits or detailed shots, you will want to focus more on aperture. 
2. Keeping your picture in mind, dial in your ISO. Start off with the low end of the spectrum (preferably somewhere around the ISO 200 mark to keep noise to the minimum). This can be increased later as needed.
3. Now it is time to select your preferred aperture. If you want to keep only your object in focus and have the background blurred at the same time, you will want to have aperture wide open - e.g., f/2.8
4. At this point, pay attention to your light meter. What does it say? If it is on the left side, you don't have enough light, and you need to compensate for this by slowing down your shutter speed. Slowly turn your dial until the triangle is at the center of your light meter.
5. As soon as the triangle touches the middle, focus and then shoot.

Voila! Now you can fully enjoy your creative abilities.

Learn More:

• Understanding Manual Mode of a DSLR Camera
• Why Shooting Your Camera in Full Auto Mode Doesn't Work

Tips When Dealing With Tricky Lighting

Of course, even with these advanced metering functions, the camera is still limited when it comes to judging the correct exposure. For times when you are shooting outdoors and your subject is much darker than the background, your camera will judge the overall light value, and you will most likely get an image in which your main subject overexposed.

Exposure Compensation Setting

The Exposure Compensation setting allows you to force your camera to compensate exposure by a number of stops. 

For example, when your subject is darker than the background, try to use +1 stop on exposure. The camera will measure the light as it did before, but now, when you shoot, it will add an extra 1 stop of exposure.

Graduated Neutral Density Filters

Another issue with exposure that you are likely to face is shooting landscapes - most times the sky will come out much brighter than the rest of an image. If you tried the Exposure Compensation setting and it’s simply not doing it for you, you might want to invest in some graduated neutral density filters.

Graduated neutral density filters are darker at the top and neutral at the bottom (well, unless you are holding it the other way around). Placing one of these filters in front of your lens works in a similar fashion as the Exposure Compensation setting would. The dark side reduces the light coming in from the sky and balances out the whole image. Pretty nifty, huh?

These filters usually come in gradients of -1 stop, -2 stops, -3 stops, and so on. To determine which one you need under different circumstances, measure the light twice:

1. First, tilt your camera down and exclude most of the sky. This will give you correct light reading for the foreground. 
2. Then tilt your camera up and exclude most of the foreground. Now you have the correct exposure for your sky. 
3. Calculate the difference between the two and select the filter that will balance out the scene.

Learn More:

• A Beginner's Guide to Aperture Priority Mode and Exposure Compensation
• The Best Filters to Have in Your Bag (and Why You Need Them)

Unleash Your Creativity

I hope that you can see why understanding light metering on your camera is important. After all, how else can you become truly free in your creative decisions unless you can fully control your tool of choice?

You don’t see painters using automated paintbrushes or sculptors using pre-made forms of clay. Same goes for professional photographers - the best art is always made from scratch!

Learn more about using your camera's light meter in the video above by Jared Polin.