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Light It Up - The Keys to Mastering Exposure

Welcome to the world of exposure- the most fundamental part of how to make your photos look awesome by adjusting the brightness, detail, and quality. Exposure is the amount of light that reaches the sensor on the camera when you take a photo. On this page, you’ll learn about the three crucial features of photography- ISO, aperture, and shutter speed- and how they work together to create good (or bad) exposure.

To help you begin to visualize this concept, here are example photos that are underexposed (too dark), well exposed, and overexposed (too bright). You’ll learn more about why their exposure settings make a difference in the final result.

Underexposed
ISO: 400
Shutter Speed: 1/125
Aperture: f/4.0

Well exposed
ISO: 1250
Shutter Speed: 1/125
Aperture: f/4.0

Overexposed
ISO: 3200
Shutter Speed: 1/125
Aperture: f/4.0

The Exposure Triangle

To understand the way that the three elements of exposure work together, there is a diagram called the exposure triangle. It is formed with ISO, aperture, and shutter speed. The triangle illustrates how these elements are connected so that adjusting one will affect the others. To achieve correct exposure, you need to find a balance between these settings, based on the light available where you are shooting, and based on what type of photo you want to achieve. Later on, I will explain how the adjustment process works.

Time To Be Fake - ISO's Artificial Light

Next, we’ll dive into the first concept that creates exposure: ISO. This is the amount of “artificial” light that the camera sensor adds to your photo. In short, it lets you increase or decrease the brightness of your photo. It’s always a good idea to set this first out of the three exposure settings, based on the environment you’re shooting in.

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When adjusting ISO on the camera, it’s shown in values from about 100 to 51200 and is set in increments of double the previous value. For example, 100 ISO, 200 ISO, 400 ISO, 800 ISO, and so on.

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My professor said to think of ISO like the number of light bulbs to bring to your shooting location. If you are shooting in a well-lit environment you may only need 200 or 400. But if you’re in a darker location like a park with lots of shade trees to block the sun, you’ll need to increase the number of “light bulbs” to about 800. Inside a building with overhead lighting, maybe 1600 light bulbs.

Here’s a quick guide to the typical ISO levels based on your environment:

  • Sunny day - 200 or 400 ISO

  • Shade/cloudy - about 800 ISO

  • Inside a room - ranges from 800-3200 (depending on lighting)

  • Nighttime football game - 3200

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Quick Warning: Raising the ISO works well to add light to the image, but higher ISO levels can give you more digital noise or grain in your photos, which you want to avoid to maintain good image quality. In this side-by-side comparison, notice how the image on the left has more fuzziness/grain, while the one on the right looks more smooth. The ISO for the left image is 25600 as opposed to only 1600 on the right.

Aperture - The Pupil of Your Camera

The aperture is the adjustable opening of the camera lens that affects how much light reaches the sensor while a photo is being taken. You can think of it like the pupil in your eye, which shrinks or expands based on the amount of light in your environment- the difference is that you are in charge of changing the aperture. It affects both the exposure and the depth of field.

Aperture is shown in what are called F-stops, which range from f/1.4 to f/32. A large/wide aperture lets in more light. Large apertures are on the f/1.4 to f/4 range of the scale. You would use a large aperture to let in more light. Oppositely, a small/narrow aperture allows less light to enter the lens. Small apertures are on the f/16 to f/32 range of the scale.

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Another key function of aperture is to affect the depth of field. This is how much of your image is sharp and in focus from the front to the back, or in other words, from the subject to the background of the image. For example, this photo was taken at an aperture of f/2.8, focusing more on the subject (the dog) and less on the grassy background. It causes the background to become blurred away and the focused area of the image to be smaller, creating what is called a shallow depth of field.

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The second image was taken with an f/20 aperture, and you can see how the focus of the image is on almost the entire contents of the frame. You can see details ranging from the front entrance of the zoo all the way to the people walking in the background. That’s because the narrow aperture focuses on the larger landscape rather than a more singular subject, creating a deep depth of field.

Two things can affect your depth of field: the aperture and the lens that you use. Aperture can have a further range of F-stops if you use a longer lens, such as a 70-200mm. With a longer lens, you can get a much shallower depth of field, like in the dog photo above. This is ideal for portrait photography.

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A good way to remember what F-stop matches what depth of field is this: imagine that the F-stop number is the number of people you are taking a photo of. For f/2.8 or similar low numbers, think of two people in a close-up shot or portrait. For f/16 or greater (f/22 or f/32), think of multiple rows of people that all need to be in focus. There are more things in focus from front to back, like a landscape.

Shutter Speed - Freezing Time

Shutter speed is the element of the camera that determines if your photos are clear or blurry. The shutter closes and opens rapidly to expose the sensor to light for a specific amount of time, usually mere fractions of a second. It can freeze motion or create blur depending on how it’s used.

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Shutter speed is measured in (fractions of) seconds. A good starting point for most subjects is 1/125th of a second. However, the faster the shutter speed, the clearer the photo will be. Having a fast shutter speed will freeze movement in the frame and will eliminate any visibility of the slight movement of the camera from shaky hands. The fastest shutter speed on most cameras is 1/1000th of a second.

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The slowest shutter speed can range anywhere from ½ a second to full minutes (60 seconds) but the longer speeds are reserved for certain types of creative photography where you want to show motion or bring in more light. These are not used for photos of everyday life. A common example of this is pictures of traffic on a busy road where all you see are the beams of light- that is motion blur where a slow shutter is used.

Some notable shutter speeds for different scenarios include:

  • 1/125th of a sec - average starting point - works for day to day shots

  • 1/500th of a sec - a good minimum for sports photography or fast motion

  • 1/1000th - the clearest possible image

  • 3 seconds - for showing motion - think traffic blur

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Pro tip #1: Your shutter speed should be equal to or greater than the focal length of your lens to prevent camera shake. So, for a 200mm lens, you need a shutter speed of 1/250th or higher.

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Pro tip #2: For shots at ½ a second or slower, you will need a tripod to keep the camera steady, since the shutter is open longer and will capture more movement.

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