Different combinations of aperture, shutter speed, and ISO can produce the same overall brightness in an image, a concept known as equivalent exposure. The unit of light change between combinations is the "stop," defined as a doubling or halving of light. To choose the right combination, photographers rely on a built-in light meter that suggests exposure settings, as well as a histogram, a graph showing the tonal distribution of an image from dark to light. A valuable technique is to "expose to the right," pushing the histogram toward the brighter end without clipping, which maximizes the data captured by the sensor and preserves detail in shadows.
When the histogram is pushed too far, detail is lost in pure black (shadow clipping) or pure white (highlight clipping). The range between these extremes that a sensor can record is called dynamic range. When a scene exceeds the sensor's range, photographers can use bracketing — taking multiple exposures at different settings — and merge them into a single High Dynamic Range (HDR) image. For quick adjustments, exposure compensation allows the photographer to bias the camera's automatic exposure brighter or darker, typically across ±3 stops in 1/3-stop increments.
Cameras offer different metering modes to evaluate a scene: matrix (or evaluative) metering reads the entire frame and works well as a default; center-weighted metering prioritizes the middle of the frame; and spot metering measures a small area for precise exposure control. Choosing the right metering mode helps the camera interpret the light the way the photographer intends, whether balancing a complex landscape or isolating a single subject.