The exposure triangle describes how aperture, shutter speed, and ISO work together to create a usable image. Each setting changes the amount of light reaching the sensor, but each also shapes the look and feel of your photograph. The trick isn’t memorizing numbers; it’s deciding what visual priority matters most and adjusting the other two to support it. Start by asking a creative question: Do I want background blur, motion freeze, or low noise? That answer points to your “primary” control.
Aperture is the size of the lens opening. A wide aperture such as f/1.8 or f/2.8 lets in more light and creates shallow depth of field, which suits makeup and portrait work because it isolates the face and smooths distracting backgrounds. A narrow aperture, say f/8 to f/11, lets in less light but increases depth of field, keeping landscapes crisp from foreground to horizon. In travel scenes with strong foreground elements—rocks, flowers, signage—stopping down helps hold detail across the frame.
Shutter speed controls how long the sensor is exposed. Fast speeds like 1/500s freeze gestures and eyelashes, perfect for portraits or candid street moments. Slower speeds like 1/10s to several seconds record motion as blur—waves become silk, crowds become streams of light, and waterfalls feel dreamy. When handholding, a simple guardrail is the reciprocal rule: keep shutter around 1 over your focal length (for a 50mm lens, ~1/50s or faster) to avoid camera shake, unless you deliberately want motion trails.
ISO amplifies the sensor’s signal. Raising ISO brightens the image but also raises noise, which appears as grain and can reduce color fidelity. Modern cameras handle moderate ISO well, so don’t fear values like 1600 in dim interiors; just avoid pushing ISO so high that skin tones look waxy or night skies break apart. For clean makeup shots under soft light, keep ISO low and shape brightness with aperture and shutter, or add light rather than adding gain.
“Pick one artistic goal—blur, freeze, or clean detail—then move the other two dials to protect that decision.”
Workflow in the field: set your priority first. For a makeup portrait with creamy background, choose aperture priority (A/Av mode), dial f/2.8, and let the camera suggest shutter speed—raise ISO only if that shutter gets too slow for handholding. For a travel waterfall where you want softness, switch to shutter priority (S/Tv) and choose 1/4s with a tripod or brace; use a lower ISO and stop down slightly to avoid overexposure. Manual mode is useful when light is constant and you want repeatable results across a sequence.
- Use your meter and histogram; expose to protect highlights in skin and sky.
- Stabilize: tripod, wall, or elbows tucked in for slower shutters.
- In mixed light, set white balance deliberately—auto can drift mid-shoot.