A densitometer is a specialised instrument used to measure the density of an image, particularly the amount of silver deposits in developed photographic film or prints. It works by analysing how much light is either transmitted through (for negatives and transparencies) or reflected from (for prints) the image. Densitometers are commonly used in professional darkrooms, printing labs, and quality control processes to ensure accurate exposure, consistent tonal range, and precise reproduction of images. Understanding and using a densitometer helps photographers achieve greater control over contrast and image quality.