Light is a Currency [Digital Photography]

All You Need to Know

Let’s presume that you want to take a crisp, deep photograph of a fast-moving subject—for example a player in a sports game, a fluttery bird, or a sexy celebrity who you’re shaking with nervous excitement to meet—well that picture is gonna cost you. Light is the currency you use to buy a good picture, and since light is very limited you’ll need to spend it wisely to get the most out of it.

There are two main things you can spend your light budget on:

Shutter Speed

Fast shutter speed produces crisp, blur-free images of moving subjects and it compensates for any shaking in the camera. Faster-moving subjects require faster shutter speeds to capture clearly, but the higher your shutter speed the darker the photo appears, so it’s best not to use any higher shutter speed than necessary.

Aperture

Higher aperture value (or F-stop) produces greater depth to the photograph. This depth is generally what makes a photo look “professional” or “cinematic,” but the higher the aperture value the darker the image appears.

Budgeting Light

Photography influencers will often say it’s best to shoot pictures in manual mode to learn how the camera works, and while there is some truth to that it’s important to understand why. When shooting in manual, you are forced to budget your light on your own, and make tough decisions about the balance you want to strike between shutter speed, aperture, and brightness. This can be overwhelming though, and it certainly overwhelmed me, so instead I advocate for learning via the shutter speed and aperture priority modes. In shutter priority mode, you control the shutter speed and the camera automatically sets the aperture to a number it thinks is appropriate for the light level. Aperture priority mode works the same way, but with you controlling the aperture and the camera controlling the shutter speed. Playing with these modes as a way to see what a balanced light budget looks like is a great way to learn how to budget light for yourself, and the priority modes continue to be great shortcuts if you’re shooting pictures on the fly.

Taking Out Loans (ISO)

ISO is the number assigned to the sensitivity of your camera’s photo sensor, so increasing the ISO increases the amount of light you have available to spend, but it comes with a catch. High ISO values introduce digital noise that looks like static into the image, which is why professional photographers advocate for shooting at the minimum ISO whenever possible. This is technically correct, but highly impractical advice. In real life you’ll often shoot pictures in dark environments, and increasing the ISO to give yourself enough light to work with is often a necessity. When choosing an ISO value just try not to set it any higher than necessary for the picture you’re trying to take, since image noise from high ISO can only be edited out to an extent.

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If You’re Curious

Modifying shutter speed, aperture, and ISO can also be used for all sorts of artistic effects.

Low shutter speeds can be used to produce artfully blurry pictures of moving subjects or used to paint images with light. When used with a stable tripod, low shutter speeds can also be used to make dim objects like stars and the moon appear much brighter in a photograph.

Likewise, low aperture values can be used to flatten images to make it look like two subjects that are far apart are actually right next to each other. This is how the particularly convincing images of people holding up the Leaning Tower of Piza are made. Particularly high aperture values can also be used to produce a background blurring effect behind a nearby subject (called bokeh), which is now commonly created artificially using photo editing software.

Lastly high ISO can be used to produce a “deep fried” grainy look to an image to emulate cheaper or older cameras for spooky or comedic effects.

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