A group of more than 50 New Yorkers gathered last night in Herald Square for an after-dark walking tour. They came to hear about the difference between high pressure sodium (HPS) and metal halide (MH) lighting from Howard Brandston, one of this country’s leading lighting designers — and to see the difference for themselves. The City is in favor of HPS lights to save energy, money, and lessen light pollution of the night sky. The streetscape committee at MAS favors MH.

Under HPS lights on Eighth Avenue, fair-skinned people looked yellow, evergreens appeared brown and dying, and primary colors (held aloft on colored foam core boards) turned muddy and difficult to distinguish. Howard Brandston described HPS lighting as appropriate for roadways and highways, but not for a city which (as Lewis Mumford wrote) “…exists not for the passage of motor cars, but for the care and culture of man.”

Under the white light of MH on 34th Street., people looked attractive, food looked appetizing, and merchandise was appealing. Howard made the point that we shouldn’t depend on light meters to decide what our lighting should be: a light meter doesn’t detect color and it can only measure units of radiant energy — not how well a human being can see nor what the nighttime world looks like.

In his view, the best way to save energy and money and reduce light pollution is to stop over-illuminating our city streets. Howard took multiple foot-candle readings (a foot-candle is the amount of light one foot from a candle) ranging from directly under a street lamp to the middle of Bryant Park. In Bryant Park, we could see each other’s faces clearly and read a tour brochure. The reading was 0.2 foot-candles. Mozart could follow a musical score, Howard explained, in a setting that was 2.0 foot candles. Elementary schools in this country were once lighted to 5 foot-candles. In the 1950s, the standard became 70 foot-candles. It appears we waste a lot of watts.

To learn more about HPS and HL, listen to Howard Brandston’s podcast interview from last week here or read a paper he delivered at a conference in Toronto in the 1990s here. Toronto, considered one of the world’s most livable cities, chose metal halide for their street lighting system. To find out why, walk from the white light of Herald Square north to 38th St. and then west to the yellow light of Eighth Ave. and back. Let there be (white) light.