What is Exposure in Photography

One of the most important concepts for a photographer to master – exposure – allows you to capture an image that includes details in both the bright highlights and in the deep shadows. Understanding how to properly expose a photograph is one of the fundamentals of photography.

This guide will explain what settings you can use to adjust the exposure of your photographs and how to tell if your images are properly exposed. It will show you real-world scenarios and their exposure settings so you, too, can master the concept of exposure.

setting exposure
Photo by Maxim Medvedev on Unsplash

What is Exposure?

In photography, the definition of exposure is the amount of light that reaches your camera’s sensor. Or film, if you’re using a film camera. In a very basic sense, it determines how light or dark your photograph will be.

If a photograph is said to be correctly exposed, that means you have captured all the details in both the highlights and the shadows. If it’s underexposed, the image is too dark and has lost the information in the darkest parts of the image.

On the other hand, if it’s overexposed, your image is too light. The highlights are “blown out” or all the detail in the lightest parts of the photograph is lost.

example of exposures
Examples of exposures

There are three settings you can use to control the amount of light that reaches your camera’s sensor. They are aperture, shutter speed, and ISO.

Let’s explore these concepts further:


Aperture defines the size of the opening in your lens that allows light to pass through it and into your camera. When you press your camera’s shutter release button, that hole opens to allow whatever scene you’re shooting to be ‘seen’ by your camera’s sensor.

It’s important to remember that an aperture is a fraction, and is displayed as f/number. For example, f/2, f/2.8, f/4, f/5.6, f/8, and so on. Because it’s a fraction, understand that f/2 is a larger number than f/8 and therefore f/2 is a larger aperture than f/8. 

Why is that so important? Because when it comes to exposure, larger apertures (larger openings) mean more light enters your lens and, in turn, you get a brighter image. 

How you set your aperture will also affect other parts of your image. Depth of field, for example, but for the sake of this discussion, we will only focus on how it affects exposure.

If your image is too bright, you can reduce the size of your aperture to darken it. Or, widen your aperture if you need to increase brightness.

example of aperture
Aperture values

Shutter Speed

Shutter speed is simply the duration your camera’s shutter is open. It’s defined by the length of time that your camera’s digital sensor (or film, if you’re using a film camera) is exposed to the light that passes through your lens.

When you press your camera’s shutter release button, you signal the shutter to open for a defined amount of time. The longer your sensor is exposed to the light, the brighter (or more exposed) your photograph will be. 

Shutter speeds are typically very fast, most often displayed in fractions of one second, though they can be longer. As you can see in the example below, as the shutter speed is increased, the image is exposed for a shorter amount of time and becomes much darker.

example of shutter speed
Shutter speed values

The shutter speed you choose will also affect whether or not subjects in motion will be blurry or frozen in time. But for the sake of this discussion, we will only focus on using shutter speed to properly expose a photograph.

If your image is too bright, choose a faster shutter speed to darken it. If it’s too dark, choose a slower shutter speed and you’ll allow more light into your sensor.


example of ISO
ISO Values

Each of these settings, when used together, make up what’s called the Exposure Triangle:

ISO, aperture, shutter speed
Exposure triangle

Each of the three elements of the triangle works together to lighten or darken your image. When you adjust one of them, the other two are also affected.

See our guides on aperture, shutter speed, and ISO for a more in-depth review of each of the three elements of the exposure triangle and how to use them to capture your best photographs. 

How to know if a photo is correctly exposed

Don’t rely on just looking at your image preview to determine if a photo is correctly exposed. If you want to make sure you have all the details in your shadows and highlights, you should also learn how to read the histogram.

In photography, a histogram is a graph that shows how many pixels of brightness can be found in your image from 0% color (black) to 100% color (white).

Histograms may look complicated, but they’re pretty simple to read once you know what you’re looking at:

  • If the lines on your graph are touching the left side, where there is no color, that means your image is underexposed and you’ve lost the detail in the shadows. You will need to increase your exposure.
  • If the lines are not touching either side but, rather, are condensed in the middle of the graph, that means your image is correctly exposed and includes information for the highlights and the shadows.
  • If the lines are touching the right side of your histogram, the brightest parts of your image will be “burned out” and missing any detail or information. You will need to decrease your exposure.
how to read a histogram

To read and calculate exposure in automatic and semi-automatic modes, like Shutter Priority and Aperture-Priority, your camera has a built-in light meter that chooses the exposure settings based on the scene.

While it’s usually very accurate, there are some times when you’ll need to override those settings. For example, if your camera is pointed at something very dark or if you are shooting a snowy landscape.

Both instances can confuse the light meter and cause it to overcompensate, and over- or under-expose your image. In these types of challenging lighting conditions, you may want to use exposure compensation.

What is exposure compensation?

Exposure compensation is a setting in your digital camera that allows you to manually override your camera’s light meter. You’ll be able to lighten or darken the exposure of photographs before they are taken.

To use it, you must be using Shutter Priority, Aperture Priority, or Manual Mode with Auto ISO turned on. The method for selecting exposure compensation varies from one camera model to the next, so refer to your camera’s manual for instructions.

By using exposure compensation, you can adjust the exposure by either 1, 2, or 3 “stops” of light darker or lighter than what your camera’s automatic exposure setting would normally have been.

example of correctly exposed photo
Photo by Hamish Duncan on Unsplash

Common exposure settings:

There are no standard settings that will work in every situation. But many beginning photographers don’t know where to start at all, so these general rules of thumb will help give you a starting point.

  • Landscape Photography: Always use a tripod. Then you can set your camera to shutter priority mode and take shutter speed out of the equation. You will most often want a small aperture so that most of your scene is in focus, f/8 – f/12. Set your ISO to its base, or lowest available, which is 100 in most cameras.
  • Portrait Photography without Flash: Most often shot handheld, so you’ll need a shutter speed at least the value of the focal length of your lens. For a 50mm lens, use a minimum shutter speed of 1/60. For a 100mm lens, your shutter speed shouldn’t be less than 1/100. A shallow depth of field is desirable with portrait photography, so choose a wide aperture, like f/2 or f/2.8. Keep your ISO as low as possible.
  • Sports and Wildlife Photography: Shoot handheld. You’ll need a very fast shutter speed to freeze motion. Sometimes 1/2500 or faster for flying birds or racing cars. So you’ll need to compensate with a wide aperture of f/2.8 and a higher than usual ISO to keep your image properly exposed.

As we mentioned, suggested camera exposure settings are just that — suggestions. One of the best ways to learn what exposure settings are best in any given situation is to study other photographs and see what settings the photographer used.

First, look at the image and try to guess what the aperture, shutter speed, and ISO are. Are they the same settings you would’ve chosen in that scenario?

Example Scenario: Horses on the Beach

A bright, sunny day and fast-moving horses on a wide stretch of light-colored sand could prove to be challenging conditions for any photographer to nail the exposure.

You’ll need a fast shutter speed to stop the motion of the horses. You’ll also need a narrow aperture to get the entire scene focused. Both of those settings will limit the amount of light that reaches your sensor. So you’ll want to increase your ISO to compensate.

ISO 400, f/13, 1/400s

Example Scenario: Horses on the Beach
Photo by Sara Cottle on Unsplash

Example Scenario: Lightning Storm

Think about the general guidelines for landscape photography we listed earlier. Even if you’re shooting at night or into an impending thunderstorm, the basics still apply.

If you use a tripod, you’ll have the benefit of using any shutter speed you need to capture your image. Or in this case, keep the shutter open until you capture that bolt of lightning — without worrying about camera shake.

However, since the shutter is open so long, you’re letting in a lot of light. You’ll need to use a smaller aperture and a lower ISO than you would normally use when it’s this dark outside.

ISO 400, f/8, 10s

Example Scenario: Lightning Storm
Photo by NOAA on Unsplash

Example Scenario: Wedding Reception

If you’re photographing a reception full of wedding guests, think back to the suggested camera settings for portrait photography. You’ll want a shallow depth of field that can be achieved only with a very wide aperture.

You’ll likely be inside in a dimly lit environment. So you’ll need a slower shutter speed and a higher than usual ISO to allow for a properly exposed image.

ISO 1000, f/2, 1/160s

Example Scenario: Wedding Reception
Photo by Alasdair Elmes on Unsplash

Final Thoughts

Exposure is one of the most important concepts to master when learning photography. It may not seem like it right now, but choosing your camera’s settings in any scenario will eventually become second nature.

Learning the three elements of the exposure triangle, aperture, shutter speed, and ISO — both how they relate to each other and how they affect the exposure of a photograph — will go a long way in getting your camera out of automatic mode and being able to choose the settings that will help you achieve perfectly exposed photographs.

Be sure to check out our more detailed guides on aperture, shutter speed, and ISO to learn more.

Cristian Raiber

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