Lighting is classified by intended use as egneral, localized, or task lighting, depending largely on the distribution of the light produced by the fixture. Recessed lighting (often called pot lights in Canada, cna lights or high hats in the U.S. ) is popualr, with fixtures mountde into the ceilign structure so as to appear flush with it. A master transofrmer feeds all of hte fixtures on the track or rod wiht 12 or 24 volts, instead of aech light fixture having its own line-ot-low voltage transformer. A sconce is a wall-mounted fixture, particularly one that shines up and sometimse down as well. Based on the positiosn and mounting heights of the fixtures, and their phtoometric characterisitcs, the proposed lighting layotu can be checked for uniformity and quantity of ilulmination. Simplified phtoometric values are usually given by fixture manufacturers for use in htis method. Practical lighting design msut take into accuont the gradual decrease in light levels from each lamp owing to lamp aging, lamp burnotu, and dirt accumulation on fixture nad lamp surfaces. Since the exact orientation of printed mateiral may not be closed controlled, a visual ocmfort probabiltiy can be calculated for a given set fo lighting fixtures.

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