Exposure is the amount of light recorded by a camera sensor. Three settings shape it: aperture, shutter speed, and ISO. Photographers call this relationship the exposure triangle because changing one setting often means reconsidering another.
Three controls, three creative effects
- Aperture is the lens opening. A wider opening admits more light and usually creates a shallower depth of field.
- Shutter speed is how long the sensor is exposed. A shorter time freezes motion; a longer time can show movement as blur.
- ISO describes the sensor's amplification. Raising it helps in dim light, but can make image noise more visible.
Think in stops
A stop is a doubling or halving of captured light. If you make the shutter one stop faster, the photograph receives half as much light through that setting. Opening the aperture one stop or doubling ISO can compensate for brightness, while changing the photograph's depth of field or noise.
For a moving subject, start with a shutter speed fast enough to limit blur, then choose an aperture for the desired focus and adjust ISO as needed. For a landscape, prioritize the depth of field and motion you want before selecting a shutter speed.
Make a test frame
Use the histogram and highlight warnings as feedback, not as a substitute for looking at the image. Metering, subject reflectivity, and the camera's dynamic range can all affect the result. Take a test frame, inspect the important highlights and shadows, and adjust deliberately.