Mixing Streetlamps.

[spuffock]

Playing around with a bit of diffraction grating, I noticed that the spectrum of low pressure street lamps consists mostly of the bright yellow sodium "D" line, whereas the high pressure lamps show a continuous spectrum, with a black line where the "D" line ought to be, due to absorption by the cooler sodium vapour around the arc. I was wondering if anyone has tried mixing the light from the two types of lamp in an attempt to produce white, and what results they obtained?

 

[RODALCO]

I think you answered your own question.

One type is Low Pressure while the other type is High Pressure.

The HP lamp has some mercury added which causes the more peachy colour and improves the colour rendering of the lamp.

To obtain white light with a little blueish tinge Mercury Vapour lamps are used.

 

[rjvh]

i am not aware that sombody (manufactor) did, but in general the yellow have a bigger watt to lumen ratio and also a better contrast result
that's the reason that they widely used in street lighting

the white lighting is more used in factory halls and big open air working spaces as colors are better represented in the spectrum and it's a lesser strain on the interpatation for the human brain (People work better and are more concentrated)

Robert-Jan