How Exposure Works in Photography
In photography, exposure is how dark or light a photo is. A natural-looking photograph—or, at least, one that appears as the photographer intended—is said to be correctly exposed. However, one that’s too dark is underexposed, and one that’s too bright is overexposed.
Exposure is controlled by the shutter speed, aperture, and ISO settings on a camera. You don’t have to stress about these, though (unless you want to) because your smartphone takes care of it all.
Within a single photo, there’s a limit to the range of exposure values (called stops) that can be captured. How broad the dynamic range is will depend on the camera you’re using. DSLRs and professional cameras can capture more than smartphone cameras. There’s also a limit to the range of values that can be shown on a screen or recorded in a single image file.
What’s important (for our purposes, anyway) is the range between the darkest and brightest colors your smartphone can capture or display is narrower than what the eye can see. This is why you can see people clearly at sunset, but your iPhone will record them as silhouettes to correctly expose the sunset, as shown in the image above.
Since your smartphone can’t capture everything in one photo, it has to decide what to prioritize every time you press the Shutter button. Most of the time, it works really well, but some things can throw it off.
Before you take a photo, your smartphone measures how bright or dark the scene is, and then guesses which exposure settings to use. However, it always assumes that everything averages out to a middle gray.
This is actually a pretty good assumption—especially when backed up with machine-learning algorithms that recognize a wider range of situations, but can still get confused.
This might seem a bit too technical, but it’ll make troubleshooting why your photos aren’t turning out the way you want a lot simpler.
RELATED: What Is Exposure Compensation in Photography?
You’re Shooting Something Really Dark
If you’re taking a photo of something dark—especially if it’s prominent in the frame—your smartphone will likely overcompensate. In other words, it’ll brighten everything too much and overexpose the photo.
In the physical world, the Powerbeats headphone case in the image above is black. However, in the photo, it looks like it’s a muted grey. The iPhone overexposed the shot because it didn’t think it was photographing something that dark.
You’re Shooting Something Really Bright
If you’re trying to take a photo of something that’s really bright, you’ll get the opposite of the above result, which is an underexposed photo.
In the photo above, the iPhone assumed the light bulb wasn’t as bright as it really is and darkened the rest of the photo accordingly. It didn’t turn out too bad in this case, but this can be a problem whenever you’re shooting things against a bright background.
Your Smartphone Is Metering from the Wrong Thing
Your smartphone’s camera uses a light meter that attempts to define the correct exposure settings, but it doesn’t always meter from the whole image. In fact, it has different metering modes that prioritize things in the center of the image or objects that seem important.
Sometimes, this causes it to meter from the wrong thing. For example, if the subject of your photo is standing near the edge of the image, your smartphone might meter from the brighter center. The result will be an underexposed image.
On most smartphones, you can tap the screen to focus and tell the camera from where it should meter. If you accidentally tap a bright or dark area of the frame, this can mess up your shots.
RELATED: What Are the Different Metering Modes on My Camera And When Should I Use Them?
There’s Not Much Light
Smartphone cameras have very small image sensors, which is what makes them so compact. However, this also means they struggle to gather enough light at the best of times.
Your eyes perform much better in low light. So, even if you can see clearly, there might not be enough light for your smartphone’s camera. If you’re taking photos in low light, there’s a good chance they’ll come out way too dark.
It’s Too Dark When You Print It
Sometimes, you might have what looks like a great photo on your smartphone, but when you print it, the same image looks dim and drab. There are a few things potentially going on here, but a big part of it is your smartphone’s screen is backlit, but paper isn’t. This means every photo will look brighter on your phone than it will when it’s printed.
For some tips on overcoming this problem, check out our guide on the subject.
RELATED: Why Do Photos Look Different When I Print Them?
How to Nail the Exposure Every Time
Regardless of why your photos are incorrectly exposing, there are some things you can do to stop it from happening. Understanding why it’s happening will help you figure out the best work-around.
Here are some things you can consider or try:
Think about the photo you’re trying to take: Smartphone cameras are better than ever, but they aren’t perfect. They can still mess up when left completely to their own devices. If you’re trying to capture a shot that’s particularly dark or bright, just pay a bit more attention. Tap the object off of which you want the camera to meter: On almost all smartphones, you can tap the screen to focus on your subject. It’ll also then adjust the exposure accordingly. If you want to make sure something’s properly exposed, tap it! Use the exposure controls: Every smartphone camera also has some built-in basic exposure controls. Some even have more advanced options. Normally though, you just tap what you want to focus on, and then drag your thumb up to increase the exposure or down to decrease it. Do this to get the best exposure before you take your photo. Use high dynamic range (HDR): This merges different exposures together in one image. iPhones now take HDR images by default whenever you shoot in high-contrast lighting. On most other phones, there should be an HDR setting you can enable in the Camera app. It might not always look good, but in some cases, you’ll get the best shot possible. Take several shots: Give your smartphone more than one opportunity to get it right. If you miss with your first attempt, re-meter and go again. Fix things in post: Most digital photos benefit from a little editing. If your image is only a little under- or overexposed, fix it in your favorite editing app—even Instagram will do!
