lamps on a street west of Chicago about
40 years ago. There were very orange .... like a pumpkin.
The high pressure sodium lamps of today do
have some other colors present to make them less
objectionable, i.e.whiter (but not much). I know this
probably doesn't answer your question, but one could draw
some parallels and hypotheses.
High-Pressure Sodium Vapour lamps have a mostly a pale red orange
Even more efficient for streetlighting is the Low Pressure Sodium
Vapour lamp. It produces a bright yellow light.
I was in Chicago 20-30 years ago when they used to put the Low
Pressure Sodium Vapour lights at certain intersections. These were
The main and side streets had the orangy HP Sodium Vapour lamps, and
the alleys, which were illuminated by an order from the late first
Mayor Daley, had the sickly blue Mercury Vapour lamps. Anyone know if
they still do this? I think the rumour was for Chicago to put the
old Mercury Vapour lamps in the alleys as a cost saving measure until
the bulbs were used up.
The lighting effect when viewed from a high building like the Sears
Tower or the Hancock building was spectacular. An endless grid of
light squares stretched out in the distance and you could clearly
trace the alleys vs. the main streets.
Lower Wacker Drive had some famously spooky green lighting. I'm not
sure what type was used for this, but it was a weird color.
Here is a good link on the characteristics of the low pressure sodium
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