Exposure Value (EV) is a numerical scale used in photography to indicate the sensitivity range of a TTL (Through-The-Lens) or off-camera light meter system, showing the combination of shutter speed and aperture settings within which accurate exposure measurement is guaranteed. Each EV step corresponds to a doubling or halving of the amount of light reaching the film or sensor, making it a convenient way to quantify exposure and compare lighting conditions. Photographers use EV to quickly assess how a scene can be captured with correct brightness while maintaining desired depth of field and motion control.
Understanding EV is important for both manual and automatic photography, as it allows photographers to predict how changes in lighting or camera settings will affect the final image. By using EV, photographers can make informed decisions on exposure adjustments, exposure compensation, or bracketing, ensuring consistently well-exposed images under a wide variety of lighting conditions.