sensitometer

A sensitometer is a scientific instrument used to measure the sensitivity of photographic materials to light. It works by exposing a piece of film or photographic paper to a carefully controlled series of light intensities. This is typically achieved by passing light through a step wedge, which has a series of neutral density filters of varying opacity. Each step of the wedge exposes a different portion of the photographic material to a progressively lower light level. Following exposure, the material is developed according to standard procedures. The resulting image will show a gradient of densities. A densitometer is then used to measure the optical density of each exposed step. By plotting the density against the logarithm of the exposure, a characteristic curve, also known as the H&D curve, is generated. The shape and position of this curve reveal information about the material's sensitivity, contrast, and maximum density. Different types of sensitometers exist, including those that use intermittent exposures and others that use continuous exposures, each suited for specific types of photographic materials or applications. Sensitometers are crucial tools in photographic research, quality control, and the development of new photographic technologies.