For over 60 years, Photo Research has had a reputation of manufacturing world class photometers that serve the markets ranging from aerospace to agriculture. The PR-810 is one in the new family of filter photometers that further extends and enhances our reputation. As with all our photometers, the PR-810 features the Pritchard optical system for unparalleled target alignment. With the Pritchard system, the alignment and measuring optics are one in the same, so there is no misrepresentation of what is being measured.