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What Is Exposure? (A Beginner’s Guide)

Every advanced and professional photographer today absolutely needs to learn how to use exposure in photography. When you first start taking pictures, you might be confused by the countless buttons and menu options on your camera. However, there is no excuse for using a bad in-camera exposure.

By understanding how to expose an image properly, you will be able to capture photographs of the ideal brightness, including high levels of detail in both the shadows and highlight areas. This article explains exposure in detail, as well as helping you understand the three most important camera settings of all: shutter speed, aperture, and ISO.

Watch camera settings carefully

Amazing conditions mean that you have to be very careful with your camera settings, especially exposure. 1/800 second, f/2.8, ISO 800.

What Is Exposure in Cameras?

In photography, exposure is the amount of light which reaches your camera sensor or film. It is a crucial part of how bright or dark your pictures appear.

There are only two camera settings that affect the actual “luminous exposure” of an image: shutter speed and aperture. The third setting, camera ISO, also affects the brightness of your photos, and it is equally important to understand. Also, you can brighten or darken a photo by editing it in post-processing software like Photoshop on your computer.

It sounds basic, but exposure is a topic which confuses even advanced photographers. The reason is simple: For every scene, a wide range of shutter speed, aperture, and ISO settings will result in a photo of the proper brightness. You haven’t “mastered exposure” once you can take a photo that’s the right brightness. Even your camera’s Auto mode will do that most of the time. Instead, getting the proper exposure for a photo is about balancing those three settings so the rest of the photo looks good, from depth of field to sharpness.

If you really want to master exposure, reading about it isn’t enough. You also need to go out into the field and practice what you’ve learned. There’s no quick-and-dirty way to pick up a skill like this. But if you can lay a solid groundwork, you’ll be at a huge advantage when you go out and practice it for yourself. The goal of this comprehensive article is to teach you all the basics that you need to know about exposure.

Shutter speed

We’ll start with a good one. Shutter speed isn’t particularly difficult; it is just the amount of time your camera spends taking a picture. This could be 1/100 of a second, or 1/10 of a second, or three seconds, or five minutes. Some people build custom cameras that take decades to capture a single photo.

Your camera won’t let you take a decades-long photo. Instead, the longest allowable shutter speed tends to be around 30 seconds, although it does depend upon your camera. For example, on the Nikon D850, you can shoot any shutter speed from 1/8000 second to 30 seconds, as well as a time mode for even longer exposures. Other cameras generally allow similar settings.

So, why does shutter speed really matter? There are two main reasons:

First, as you would expect, a long shutter speed (several seconds) lets in a large amount of light. If you take a normal daytime photo with a 30-second shutter speed, you will capture an image that is completely white. The opposite is true, too; a quick shutter speed only lets in a small amount of light. If you take a photo at night with a 1/8000-second shutter speed, the photo will be completely black.

Take a look at the series of examples below. Here, 1/25 second was too dark (“underexposed”), and 1/3 second was too bright (“overexposed”). This should give you an idea of the brightness differences with shutter speed:

Image brightness changing with shutter speed

Second, the only other big effect is the motion blur in your images. Not surprisingly, a long shutter speed (such as five seconds) captures anything that moves during the exposure. If a person walks by, they might appear as a featureless streak across the image, since they aren’t in one place long enough for the long exposure to capture them sharply. That’s called motion blur.

By comparison, a quick shutter speed (such as 1/1000 second) does a much better job freezing motion in your photo — even something moving quickly. You can photograph a waterfall at 1/1000 second and see individual droplets frozen in midair. Without a camera, they might have been invisible.

Take a look at the images below. Here, I was taking pictures on a windy day. The foreground grass and the waves behind them were all moving quickly. As you can see, depending upon my shutter speed, there was a major difference in motion blur: