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What Is the Exposure Triangle?
The exposure triangle in photography consists of three parts: shutter speed, aperture, and ISO. In order to get a properly exposed photo, you need to make sure that all three elements are working in harmony. That means that if one element changes, the other two need to change as well.
Let’s take a closer look at the three sides of the exposure triangle in order to gain a clearer understanding of how they work together to produce beautifully exposed photos.
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, f2.8 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.
This is how sensitive your camera’s sensor is to light, expressed in a number. The higher the ISO number, the more sensitive you camera will be to light. But increased ISO will also increase digital noise in your images, so you typically want your ISO to be as low as possible as the native setting for your camera.
All three of these variables work in conjunction with one another to get the correct exposure for your images. For example if you open up the aperture to let more light in, you will need to have either a faster shutter speed or a lower ISO to compensate for this additional light.
How to Utilize Camera Modes
Your camera is the most powerful tool in helping you gain proper exposure. It has various modes which allow customizable controls over the three parts of the exposure triangle.
These are the three main camera modes:
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.
You set a specific shutter speed and the camera automatically selects the aperture. This is useful when your subject is on the move.
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 Aperture Priority and Shutter Priority have their uses, and you’ll often 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.
1. Motion Blur
In order to create motion blur in your photos, the most important element of the exposure triangle is the shutter speed. The longer your shutter speed, the more blur and motion you’ll be able to capture.
If you’re using the Shutter Priority Mode on your camera, then aperture and ISO will change automatically to comply with your change in shutter speed. But if you’re doing it manually, be sure to adjust both as well.
Both shutter speed and aperture are set up in “stops.” One decreased stop in shutter speed is equal to double the length of time the shutter is open. With aperture, a decrease in one stop is equal to a 50 percent decrease in the size of the shutter opening. The numbers are proportional, so one stop on one aligns with one stop on the other.
When it comes to ISO, you’re going to have different numbers on a film camera than on a digital camera. With a film camera, ISO is represented by numbers ranging from 100 to 6400. The higher the ISO, the more sensitive the film is to light. With a digital camera, ISO relates to the sensitivity of the image sensor. The higher ISO is, the more sensitive the camera is to light. When it comes to capturing motion blur when there’s a lot of light, using a lower ISO with a longer shutter speed will help prevent overexposure.
2. Frozen Motion
If you’re looking to freeze the action in a photo—think droplets of water suspended in the air as a dolphin jumps into the ocean—you’ll want to turn your shutter speed up instead of down. The higher the speed of the object you’re trying to capture, the higher your shutter speed should be. Try starting at 1/500 and going from there.
As with motion blur, you’ll need to adjust ISO and aperture as you increase your shutter speed. Both aperture and ISO should go up proportionately as shutter speed goes up. If you’re using Shutter Priority Mode, this will be done automatically but if you’re doing it manually, you’ll have to adjust it yourself.
3. Night shots
When you’re shooting at night, it’s a good idea to work in Manual mode and to utilize a good tripod. Your aperture needs to be lower than it would be during the day, ISO should be as low as possible, and shutter speed can be long if you’re looking for blur or shorter if you want a crisper image.
4. Depth of Field
Controlling the amount of the photo that is in focus is one of the photographer’s best tools to help draw the viewer’s eye where you want it. For example, landscapes are typically shot so that everything is in focus, so photographers will shoot at small apertures (e.g. f11 or f16).
A large aperture results in a shallow depth of field, while a small aperture results in a larger depth of field. Focal length also contributes to depth of field, with a longer focal length corresponding to a shallower depth of field.
Bokeh is one popular photography method that utilizes depth of field. When shooting bokeh, set your lens to the lowest aperture and adjust ISO and shutter speed accordingly, or use Shutter Priority Mode.
Exposure Triangle Cheat Sheet
Use the following guide to get the right exposure and effect, every time you snap a photo:
Shutter speed: How long the shutter is open, expressed as a measurement of time. 1/100 = 1/100th of a second.
Aperture: How big the opening is that lets light in, expressed in F-stops. The larger the number, the smaller the opening.
ISO: How sensitive your camera’s sensor is to light. The higher the ISO number, the more sensitive to light.
Motion blur: Longer shutter speed, lower aperture, lower ISO
Frozen motion: Higher shutter speed, higher aperture, higher ISO.
Night shots: Manual mode, lower aperture, lowest ISO, shutter speed varies based on type of image.
Depth of field: Larger aperture and longer focal length corresponds with shallower depth of field. Small aperture and shorter focal length corresponds with larger depth of field.
Exposure Triangle Apps
It’s also helpful to download a high quality app that will automatically help you calibrate the correct exposure—especially if you’re a novice photographer.
Consider the following:
- Exposure Calculator (available on both iOS and Android)
- Photo Buddy
- Photo Tools Pro
- Camera Sim
Regardless of the subject matter you wish to shoot, understanding exposure is crucial to ensuring that the image you want to create and the image you end up creating are one and the same.