Light Impressions – CMH & HPS

More personal impressions, this time from outdoor lights in Stockholm (my own photos).

Ceramic Metal Halide

In Stockholm, the inefficient cool-white High-Pressure Mercury Vapour (HPMV) street lights have now been replaced by warm-white Ceramic Metal Halide (CMH) with electronic ballasts. This incandescent-looking light has nice brightness and better colour rendition than previous lamp types, showing the environment in a more flattering light than the spooky blue-white or green-white of HPM, or shades of orange from High-Pressure Sodium (HPS).

Västerbron, Stockholm (photo: Halogenica)

Västerbron, Stockholm

Mariatorget, Stockholm

Mariatorget, Stockholm

In my opinion, this makes Stockholm once again a very beautiful city, while it also saves energy as these are much more effective. Before the light was cold and harsh, now it is warm and soft, almost romantic.

Stockholm skyline, 2012

Stockholm skyline, 2012

In this view, the only light detracting from the overall romantic impression is the extremely bright cool-white Metal Halide floodlight stuck temporarily on the construction crane (I thought its reflection in the water made an interesting comparison). Also note the decorative string of incandescent bulbs on the restaurant-ship in the centre:

Stockholm skyline 2012

Riddarholmen, 2012

Here, one can clearly see the difference between the warm-white CMH lamps to the left, and the somewhat dysmal cool-white Mercury Vapour lamps to the right (in real life, the light from the latter seemed not quite as green, but cooler than cool-white and not attractive):

CMH vs HPMV, Södermälarstrand, Stockholm

CMH vs HPMV, Södermälarstrand, Stockholm

High-Pressure Sodium

I’m glad to see the most of the horrid monochromatic (orange-yellow) Low-Pressure Sodium (LPS) lamps on highways having been replaced by the more peach-coloured High Pressure Sodium (HPS) with better, though far from optimal, colour rendition. Ceramic Metal Halide (CMH) would look nice on highways too but that is not practical as they don’t last as long as HPS lamps. Here, on Söder Mälarstrand, Stockholm, the difference between the band of orange-yellow HPS street lights to the right, and the clear warm-white CMH lamps at the bottom, is clearly visible (though this picture is not the best; in reality the first is more orange and the latter more clear-white):

CMH vs HPS, Södermälarstrand, Stockholm

CMH vs HPS, Södermälarstrand, Stockholm

One place I really like HPS is in road tunnels, where they add some warmth to the often cold dark concrete – if the lamps are placed along the tunnel walls and not at a glaring angle.

HPS in Tunnel, Häggvik, Stockholm

HPS in tunnel, Häggvik, Stockholm

Improved High Pressure Sodium 

The beautification of the Stockholm lightscape began in the 1990s, when some of the oldest parts of Stockholm, such as Old Town and parts of Södermalm, received old style wall lanterns, lit by improved quality High Pressure Sodium ‘White SON’. These frosted bulbs are still in use and give a very beautiful light as they have a special diffusing layer which makes the light visibly radiate, and their warm glow is reminiscent of incandescent or even gas lights, but brighter and more efficient – a good compromise between romantic and functional.

Old style lantern, Södermalm, Stockholm

Old style lantern, Södermalm, Stockholm

HPS White SON, Södermalm, Stockholm

HPS White SON, Södermalm, Stockholm

However, these White SON are not as efficient and as other HPS lamps (quality and quantity are usually trade-offs) so EU wants to ban them, which is stupid on so many levels as they are still much more effective and long lasting than traditional incandescent lamps that would be used in such luminaires and are only used in a few select places meant mainly for pedestrians, tourists and people in love.



  1. July 3, 2012 at 11:04 pm

    Actually, those HPMV lamps really are green/white as in your picture. The human eye/brain is just pretty good at making them look rather more attractive (less green). The camera pretty much shows it the way it is relative to the CMH lamps as the auto-white balance of the camera pics the CMH lamps as a white point, and then you can see the real color of those nasty things.

    HPMV lamps are also really nasty to the environment, and ones that have broken outer envelopes radiate UV like mini-suns, a nasty luminary that we should really get rid of, sooner rather than later.

  2. halogenica said,

    July 3, 2012 at 11:48 pm

    I see! I didn’t know about the green-ness, or about how cameras work. And I think you’re right that they are Mercury Vapour lamps rather than Metal Halide as I first assumed, I’ll change the caption right away.

    I did know about the UV radiation if they break, but had forgotten that point – thanks for reminding me! That means it’s extra stupid to use them in low outdoor luminaires where drunken teens can break them for sport.

  3. May 1, 2014 at 12:03 pm

    We’re seeing the widespread introduction of Philips Stela LED lights across a part of West London and the results are very unpleasant indeed. The light is a very harsh white, achieved it seems with a high element of blue spectrum. The intensity is so great it’s even reached the BBC news

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