General Lighting FAQs

Ever wonder exactly how the human eye perceives light, how to plan a “group relamp” in a commercial setting, or the difference between backlighting and indirect lighting? These General Lighting FAQs will explain it all.

Backlighting

Q: What is the purpose of backlighting?

A: The backlighting of transparency graphics can create an unparalleled visual impact — an impact that may stay with the viewer for weeks if not months. The backlighting of white or colored translucent panels, with or without a pattern, can create a dramatic visual effect especially if there is very little light in the space coming from other sources. This type of visual effect is generally used to create a certain mood or ambiance … read more >>

Indirect Lighting

Q: What is indirect lighting?

A:  Indirect lighting is a form of lighting whereby one cannot see the light bulbs directly. It often emanates from near or off of the ceiling – sometimes in ledges, valances, or horizontal recesses on the upper wall or in the ceiling itself or from a fixture that directs the light up toward the ceiling … read more >>

Human Reaction to Lighting

Q: What is the range of dark and very bright lighting conditions over which the human eye can operate? 

A: From the darkest to the brightest conditions, the human eye can operate over roughly a ten-trillion fold (10 to the thirteenth power or 10,000,000,000,000) range of illuminance.

Q: How much can you lower light levels before occupants recognize it? 

A: Research indicates that levels can be gradually dimmed 30% over 5-15 minutes without occupants perceiving any change.

Installation & Maintenance of Lighting

Q: Should I ever install a light bulb into a socket with the electricity on?

A: Never put a lamp (light bulb) into an energized socket; turn off the electricity first to avoid premature lamp failure.

Q: For a commercial or industrial setting with a large number of lamps when is the best time to “group relamp”?

A: For a large number of lamps you probably should relamp fixtures as a group at about 70% to 80% of  rated life. This will greatly reduce the cost of the labor associated with replacing the lamps.

Q: Is it ever all right to run lamps at voltages just slightly higher than their rating?

A: No, do NOT run lamps even slightly above their rated voltage. Example: In a high-end restaurant, 75-watt halogen PAR lamps lasted only about half of their rated 2,000 hours costing the owner $900 annually. Voltmeter checks showed the sockets ran about 126 volts, five percent higher than the 120 volts standard, which significantly shortened lamp life. High voltage only in parts of a facility is probably due to internal wiring problems,that require the help of an experienced electrician.

Q: Is there a “best way” to position bi-pin fluorescent lamps in their sockets to avoid problems?

A: Yes. Example: In an office building lighted by several hundred 4-foot fluorescent fixtures, the white lampholders, or tombstones, in about 50 fixtures appeared “toasted”. Why? The fluorescent lamp pins had not been fully rotated into the tombstones’ recessed grooves, and high resistance across the poor connection caused electrical heating that cooked the holders. To avoid this problem be sure that both pins are in the lampholder AND that the lamp is rotated so that a line marked on the endcap of the lamp is lined up exactly between the two recessed grooves.