The Exposure Triangle
In photography, the exposure triangle explains the relationship between shutter speed, ISO and aperture. Whether you’re shooting old school film or with a mirrorless, these three factors are at the center of every exposure.
Understanding the exposure triangle, also called the photographic triangle, will help you determine how a picture will look before you take it. And while saving film in today’s digitally dominated world is probably not your first priority, knowing how aperture, shutter speed, and ISO work together to compose your image will make you a smarter, more efficient photographer.
With getting to know these variables, you’ll also come to realize that, at least artistically, there is no one ‘correct’ exposure for a scene.
First, what is photography, anyway? Without waxing philosophical, and just looking at its etymology, photography, literally means, “light painting.”
So, to ‘paint’ what you’ve visualized in your mind’s eye, that is, to turn your creative concept into a concrete image, it helps to understand this relationship of aperture, shutter speed and ISO, and how it affects the way light enters the camera lens and reaches the sensor to ‘paint’ your image.
Let’s take a quick look at each of the three values in the exposure triangle:
Like the iris of your eye, the aperture blades on the lens of a camera control how much light is let into the camera lens. The amount of light that reaches your camera’s image sensor will determine what the exposure looks like.
Each aperture setting on the lens is referred to as an f-stop, a fraction that indicates the diameter of the lens opening. Aperture also determines the depth of field and sharpness. Every lens has a “sweet spot” or “critical focus,” usually between f/4 and f/11.
While aperture determines how wide the lens opening is, shutter speed determines how long the lens stays open for, letting the specific amount of volume of light into the sensor determined by the aperture. A faster shutter speed, like 1/1000th of a second, has the effect of freezing motion, while a slower shutter speed, like 1/60th, will blur motion in a scene.
ISO is the international standard of measurement that determines how sensitive a photographic film emulsion or digital sensor is to light. The higher the ISO, the more sensitive the film or digital sensor is to light, and vice versa. A higher ISO will introduce more grain, or noise, into an image, while a lower ISO will produce less noise. ISO directly impacts both shutter speed and aperture.
To produce a photograph you are using the exposure triangle, balancing aperture, shutter speed and ISO, to control how long and how much light enters the camera sensor. But to make a work of ‘art,’ as it were, you’ll need a fine-tuned combination of technical prowess (i.e. knowing the exposure triangle) and an untethered imagination.