In photography, a factor is a numerical value that indicates how much exposure must be increased to compensate for a loss of light. This concept is commonly used when employing filters, lens attachments, or other accessories that reduce the amount of light reaching the film or sensor. By applying the correct factor, photographers can adjust the shutter speed, aperture, or ISO to maintain proper exposure despite the light reduction.
Understanding exposure factors is important for achieving consistent results, especially when using neutral density filters, polarizers, or other light-modifying equipment. Correctly calculating and applying the factor ensures that images maintain accurate brightness and tonal quality, helping photographers manage challenging lighting conditions and creative effects without compromising image quality.