Illuminance is a photographic term that quantifies the amount of light falling on a surface or subject. It is measured in lux or foot-candles and helps photographers understand how brightly a scene is lit, which is essential for selecting the correct exposure settings.
By measuring illuminance, photographers can accurately control exposure, achieve consistent lighting, and avoid underexposed or overexposed images. This concept is particularly important in studio photography, architectural photography, and any situation where precise lighting measurement is needed to maintain image quality.