Section 155.4. Brightness

The maximum brightness of the sign lighting shall be determined by two separate tests:

(1) The maximum project area brightness shall be measured with a calibrated, standard light meter, located so as to directly face the illuminated portion of the sign with the center of the light meter on the same horizontal plane as a horizontal line drawn through the center of the illuminated area at a distance equal to five times the diagonal dimension of the sign. Light meter readings shall be mathematically converted to candles per square inch and footlamberts where one candle is equivalent to 452 footlamberts. The maximum limits specified in this paragraph shall not be exceeded. In determining the projected area of the sign, the entire illuminated area shall be used with no allowance made for opaque lettering.

Maximum Brightness—Projected Area

Candles, Maximum	Multiply (1 CP=140)	Footlamberts, Maximum
1 per square inch	452	452 Footlamberts

(2) The maximum spot brightness shall be measured with a calibrated, standard illuminometer, located so as to directly face the illuminated portion of the sign with the center of the illuminometer on the same horizontal plane as a line drawn through the center of the illuminated area. The maximum limit of 1,800 footlamberts may not be exceeded at the brightest point of the illuminated area.

The provisions of this § 155.4 adopted August 26, 1977, effective August 27, 1977, 7 Pa.B. 2428; renumbered May 15, 1981, effective May 16, 1981, 11 Pa.B. 1678; amended February 18, 1983, effective February 19, 1983, 13 Pa.B. 783; readopted January 8, 1988, effective January 9, 1988, 18 Pa.B. 190. Immediately preceding text appears at serial pages (80036) to (80037).