Understanding the exposure triangle is like learning the ABCs of photography. It’s a fundamental concept that every aspiring photographer must grasp to take well-exposed photos. The exposure triangle consists of three main elements: ISO, shutter speed, and aperture. Each of these elements affects exposure in its own way, and they all work together to create the final image. Let’s break it down.
ISO: Sensitivity to Light
ISO measures your camera’s sensitivity to light. The standard ISO settings often start at 100 and can go up to 6400 or higher, depending on your camera. Each doubling of the ISO number represents a “stop,” which either doubles the sensitivity or halves it. For example, moving from ISO 100 to 200 is an increase of one stop, making the sensor twice as sensitive to light.
Stops in ISO:
- ISO 100 to 200: +1 stop
- ISO 200 to 400: +1 stop
- ISO 400 to 800: +1 stop
- …and so on.
Why Stops Matter: Understanding stops helps you make quick adjustments. If your photo is underexposed by one stop, you could either double the ISO or use other elements of the exposure triangle to compensate.
Exercise: Take a series of photos at different ISO settings, keeping shutter speed and aperture constant. Observe how the image gets brighter but may introduce noise at higher ISOs.
Shutter Speed: Time the Sensor is Exposed
Shutter speed controls how long your camera’s sensor is exposed to light. It’s measured in seconds or fractions of a second (e.g., 1/500, 1/250, 1/125). Like ISO, shutter speed also works in stops. Doubling or halving the time the shutter is open changes the exposure by one stop.
Stops in Shutter Speed:
- 1/500 to 1/250: +1 stop (doubles the light)
- 1/250 to 1/125: +1 stop
- 1/125 to 1/60: +1 stop
- …and so on.
Practical Considerations: A fast shutter speed (e.g., 1/1000) will freeze fast action but may result in underexposure in low light. A slow shutter speed (e.g., 1/30) risks camera shake unless you’re using a tripod.
Exercise: Experiment with shutter speeds. Try capturing a moving object like a car or a pet at different speeds to see the effects on motion.
Aperture: The Size of the Lens Opening
Aperture controls the size of the lens opening, which in turn affects the amount of light hitting the sensor. Aperture is expressed in f-numbers (e.g., f/2.8, f/4, f/5.6). Unlike ISO and shutter speed, aperture stops are not as straightforward. Common full stops in aperture are f/1.4, f/2, f/2.8, f/4, etc.
Stops in Aperture:
- f/1.4 to f/2: +1 stop
- f/2 to f/2.8: +1 stop
- f/2.8 to f/4: +1 stop
- …and so on.
Why Aperture is Peculiar: Each full stop either halves or doubles the area of the lens opening, but the f-numbers don’t double. This is because they’re a ratio based on the diameter of the lens.
Exercise: Take photos of a stationary object, like your salt and pepper pots, at different aperture settings. Observe how the depth of field changes, making the background more or less blurry.
Understanding the exposure triangle and the concept of stops is crucial for mastering manual settings on your camera. It allows you to make quick, informed decisions to get the perfect shot, no matter the conditions.