Photography Basics: What Is Exposure? Understanding How Exposure Affects Your Photographs

Camera exposure is the overall brightness or darkness of a photograph. More specifically, it’s the amount of light that reaches the film or camera sensor when a picture is being taken. The more you expose the film or camera sensor to light, the lighter your photo will be. The less light, the darker your photo will be.

There are three ways for your camera to control the amount of light that reaches the film or the image sensor; these three together constitute the exposure triangle:

1. 1. Shutter speed: This is how long the shutter is open, expressed as a measurement of time. For example, 1/100 means that your shutter is open for 1/100th of a second. The longer the shutter is open, the brighter the photograph will be, as there was more time to let in the light. Learn more about shutter speed here.
2. 2. Aperture: This is how big the opening is that lets light in, expressed in f-stops. F-stops are counterintuitive, because the larger the number, the smaller the opening. For example, f/2.8 allows twice as much light into the camera as f4, and 16 times as much light as f11. Aperture affects the depth of field: Larger openings create a shallower depth of field, while smaller openings make more of the image in focus. Learn more about aperture here.
3. 3. ISO: This is how sensitive your camera’s sensor is to light, expressed in a number. The higher the ISO number, the more sensitive your camera will be to light. Learn more about ISO here.

Tinkering with the shutter speed, aperture setting, and ISO setting will produce different types of exposures, including:

• Overexposure: Overexposure happens when the film or camera sensor is exposed to too much light. As a result, the photograph loses highlight detail and the bright parts become washed out.
• Underexposure: Underexposure happens when the film or camera sensor is not exposed to enough light. As a result, the photograph loses shadow detail and the dark parts are almost all black.
• Long exposure: Long exposure, also called time exposure or slow-shutter photography, is a technique that captures a subject over an extended period of time. The static elements of the photo contrast with the elements in motion, which create blurs, smears, and trails. Long exposure is commonly used in night photography.
• Double exposure: Double exposure, also called multiple exposure, is a technique where the camera shutter opens twice to expose the film to different images. As a result, the photograph combines the two exposures into a single image, which are laid on top of one another.

In digital photography, you can set the camera exposure mode with the click of a button or turn of a dial. There are three main camera modes and exposure settings:

1. 1. Manual exposure: You set a specific shutter speed, aperture, and ISO. This is useful if you want complete control of your camera settings and you have time to adjust them for each shot.
2. 2. Shutter priority: You set a specific shutter speed and the camera automatically selects the aperture. This is useful when you want to control the depth of field.
3. 3. Aperture priority: You set a specific aperture and the camera automatically selects the shutter speed. This is useful when you want to control the depth of field.

Both shutter priority mode and aperture priority mode have their uses and you’ll find yourself switching back and forth, depending on what you’re shooting. It often makes sense to set your ISO to Auto when you’re shooting in these modes so that the camera has more flexibility to make decisions to get the shot right.

Sometimes you’ll be shooting in shutter priority or aperture priority mode, and because part of the frame is very dark or very light, the camera gets confused and doesn’t get the setting quite right on its own. If you switch to manual mode, you’ll have control over this. But if you’re in a hurry, you can use the exposure compensation dial on your camera to override the camera’s settings. By turning the dial, you’re telling the camera to under- or overexpose the shot, giving you the desired look.

Your digital camera may also have other pre-set exposure modes and settings for capturing specific types of photographs, including:

• Portrait mode: Sets a low F-stop value to create a shallow depth of field, allowing the focus to be on your subject. Find more portrait photography tips here.
• Landscape mode: Sets a high F-stop value to create a large depth of field, allowing the entire landscape to be in focus. Practice landscape photography techniques here.
• Sports/Action mode: Sets a low F-stop value, fast shutter speed, and higher ISO to capture an athlete or a moving subject. Learn about sports photography here.
• Night/Low-light mode: Sets a fast shutter speed, increased ISO speed, and may use the flash to better expose your subject in low light. Find more night photography tips here.

Love photography? Learn from professional photographer Jimmy Chin.