Understanding Spot Metering: A Beginner's Guide

If you've ever taken a photo where your subject looked too dark or too bright, you're not alone. That usually happens because your camera—or phone—is trying to expose for everything in the frame, not just the part you care about.

That's where spot metering comes in. It lets you measure the light in one small part of the scene—like someone's face, or a detail you want to highlight—and base your exposure on just that spot.

Instead of averaging the light from the whole image, spot metering says: "Just measure this one area." It's incredibly useful in scenes with high contrast, where you want to make sure one specific subject is correctly exposed.

Let's say you're taking a portrait of a friend who's standing in front of a bright window. If your camera meters for the whole scene, your friend might end up underexposed while the window looks perfect.

But if you meter just for their face, you'll get the exposure you actually want—even if the background ends up bright or blown out.

This kind of precision is especially helpful when you're shooting film, where you can't see your results immediately. Spot metering gives you a reliable way to get your exposure right, even when the lighting is tricky.

Spot metering helps your subject come out properly exposed—even in tricky light.

Spot metering works by measuring a small part of the scene and calculating the exposure as if that area were a medium gray. This is the baseline most meters use—what's often called "18% gray." If you're metering something darker or lighter than that, you'll need to adjust accordingly.

For example, if you point your meter at a white wall, it might try to darken it to gray—meaning your photo will be underexposed. If you meter off a dark jacket, it might brighten it too much, resulting in overexposure.

Understanding how different tones affect the meter's reading is a key part of learning how to use spot metering well. It takes a little practice, but once you get it, you'll be able to predict and adjust for these situations with ease.

Spot metering isn't just for pros. It's for anyone who wants a little more control over how their photos turn out. Once you understand how to expose for the subject you care about—especially in challenging lighting—you'll see a huge difference in your results.

It also helps build your overall understanding of how light works, which will carry over into every other part of your photography.

If you're new to metering or just want a simple tool that works, Thea is designed to make spot metering feel natural. You open the app, point your phone at the subject, and see live exposure readings. You can choose between aperture priority, shutter priority, or manual mode—just like on a real camera.

When you find the right reading, tap to lock it. This is helpful if you want to reframe your shot without losing your settings. You can even switch to the front-facing camera if you're metering for a selfie or a self-portrait.

Thea also lets you set your ISO and limit your aperture or shutter speed—especially useful if you're shooting film and want the readings to match your actual gear. And it's completely free, with no ads or clutter.