PR-810 is unlike any of our previous Photo Multiplier Tube (PMT) based photometers - it's battery powered! The Lithium-Ion battery provides more that 12 hours of continuous operation providing the ultimate in portability. It also features a full color touch screen display, and 75 mm objective focusable from 14" (355 mm) to infinity.Other hardware features include AutoSync® for automatically synchronizing to the source refresh rate insuring the utmost accuracy, an optional External Trigger Port allowing remote measurement activation from either a push button or peripheral device, a Secure Digital (SD) port for measurement storage.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.