Photomultipliers are used as the detector in many spectrophotometers. ASTM standard E387 describes methods of estimating stray light in spectrophotometers. These materials find use in specialized optical settings, such as focusing elements in research spectrophotometers. Methods have also been invented to measure and compensate for stray light in spectrophotometers. They can analyze the properties of natural scenes via digital cameras, spectrophotometers, and range finders. There are two major setups for visual spectrum spectrophotometers, d/8 (spherical) and 0/45. Some absorption spectrophotometers have automatic spectral analysis capabilities. They are therefore traditionally used as a convenient calibration standard for optical spectrophotometers. Spectral measurement devices are referred to as spectrometers, spectrophotometers, spectrographs or spectral analyzers. They are therefore used as a calibration standard for optical spectrophotometers and are available commercially. Caesium bromide is sometimes used in optics as a beamsplitter component in wide-band spectrophotometers. The price of recording spectrophotometers was substantially higher than non-recording machines. The demand for synthetic rubber caused Beckman Instruments to develop infrared spectrophotometers. Approximately 30,000 DU spectrophotometers were manufactured and sold between 1941 and 1976. UV-capable spectrophotometers are common in such laboratories.