Exposure (photography)

Exposure is the amount of light reaching photographic film or an image sensor. It is controlled mainly by aperture, shutter speed, and sensor or film sensitivity.

Aperture: The adjustable opening in a lens that controls how much light passes through it. Widening or narrowing the aperture changes the light reaching the recording surface.
ISO speed: A standardized rating of a camera sensor or film’s sensitivity to light. Higher ISO settings allow a given image brightness with less incoming light, often at a cost in image quality.
Depth of field: The range of distances in a photograph that appears acceptably sharp. Changing aperture to control exposure also changes the extent of apparent sharpness.
Underexposure: An exposure that records too little light for the intended image, often obscuring shadow detail. It is the too-dark outcome of insufficient exposure.
Shutter speed: The duration for which a camera shutter exposes film or a sensor to light. Longer exposure time admits more light, while shorter time admits less.
Exposure stop: A photographic unit representing a factor-of-two change in light or exposure. Stops quantify how much brighter or darker a setting change makes exposure.
Motion blur: Visible smearing caused by movement during image capture. Long exposure times can record subject or camera motion as blur.
Overexposure: An exposure that records too much light, often erasing detail in bright regions. It is the too-bright outcome of excessive exposure.
Exposure value: A logarithmic photographic scale representing combinations of aperture and exposure time. It expresses the light-setting combinations that produce equivalent exposure.
Photographic exposure meter: An instrument or camera system that estimates light levels to recommend exposure settings. Meter readings translate scene light into proposed camera settings.

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