General > General Technical Chat
Sign of the times
james_s:
--- Quote from: Rick Law on May 14, 2021, 08:31:04 pm ---I recall reading an article that highway/street lights in white is easier for older people to see. I can't find that article anymore.
But, it makes sense -- white comprises of the entire visible color spectrum. Anyone with decreased sensitivity to any particular color can have the rest of the color spectrum to rely on.
The most common color blindness is red-green (8% of male, 0.5% female for Northern European descent according to Wikipedia), next to that is blue-yellow. Yellow, orange, amber are colors are a mix of red and green, so it is unfriendly to decreased sensitivity to red-green. The traffic light colors are even less friendly to them, yet red-green insensitivity appears to be the most common.
It may not make any difference to most of us, but I guess only until someone runs over your dog because the street is lid with yellowish lamps.
--- End quote ---
There's also a difference in sensitivity between photopic and scotopic vision, more bluish wavelengths have an advantage at low light levels. I think the real issue though is that so many things absorb orange light which leads to the effect of a bright source spraying light everywhere but the scene is not really lit up very well. The source itself looks very bright due to orange being close to the sensitivity peak of the eye but that just serves to drown out all the orange absorbing objects in the scene and produce a bunch of glare. There has also been a tendency to over-light, high light levels do not improve visibility over more modest levels, they just create contrast between brighter and darker areas. Modern regulations requiring full-cutoff luminaires that do not emit any light above 90 degrees also create a problem of needing more of them to create even illumination and even then you end up with bright pools under the source with dark spaces between. IMO they could achieve more effective lighting while still mitigating light pollution by using lower intensity sources and focus on providing even illumination. Less total light but more of it doing something useful.
Alex Eisenhut:
--- Quote from: bd139 on May 14, 2021, 07:49:43 pm ---Oh holy crap this one annoyed me. They replaced all our gentle orange sodium lights with LEDs a few years back. I had to change the curtains in the end for blackout ones because it’s like having prison arc searchlights chasing you at night otherwise.
But a year down the line I don’t even notice any more :-//
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The worst is cycling in the evening. Everyone has the landing lights of an airport strapped to their handlebars and pointed straight ahead.
bd139:
Yeah that's a massive problem in London as a driver. While I certainly respect cyclists (as a former cyclist) it really annoys the hell out of my when someone comes flying at me on the opposite side of the road with a frigging strobe light going on. I can see you fine if it doesn't flash. >:(
Black Phoenix:
--- Quote from: james_s on May 14, 2021, 07:30:12 pm ---It's funny to hear about nostalgia for high pressure sodium, I guess it's younger folks who don't remember the nice clean white light we had before those awful orange things replaced everything in the name of energy efficiency. Now we're back to nice clean white light, in the name of even better energy efficiency. I hated HPS when they initially took over and I don't miss them one bit now that they're going away.
--- End quote ---
Well I'm 35 and at least were I lived most of my life in Portugal I saw both, the High Pressure Sodium that leave that glow in Orange, the Mercury Vapour ones with their white spectrum and now the LED. And there is still places where in the same road you find the 3 types. I hate the HPS in terms of colour but the reality is that I have the impression when driving that it illuminates the street better than the Mercury Vapour, thanks to the light spill.
LED if it is a good one is something out of the world, beating the light spill perception (or reality) of HPS and having the white glow of the Mercury Vapour ones.
Here in Shenzhen where I'm currently living, the street behind my house is all HPS Yellow/Orange and the main street LED White and the LED beat in terms of illumination and pleasing to the eyes.
james_s:
It's certainly going to depend on where you are. Here in the USA mercury vapor absolutely dominated street lighting from about the late 1950s up into the early 1980s. Some areas used clear lamps and others used phosphor coated color corrected lamps, some seemed to use whatever they had on hand at the time. LPS (SOX) that was extremely common in the UK and Europe never really caught on here, there were pockets of them in a few specific areas, particularly in the vicinity of observatories but I've never seen one on a public road up here in the Northwest. HPS started to appear sometime in the 70s and the changeover really picked up steam in the early 80s until it had absolutely dominated everywhere. Metal halide was widely used in parking lots and interior lighting of large stores and warehouses from the 80s on but it was never widely used in streetlighting. There may still be pockets of mercury streetlights in some areas, there were still thousands of incandescent streetlights from the 1920s-50s in the Los Angeles area and a few other places as recently as about 5 years ago when the last company stopped making the special 6.6A series lamps. I'm sure pockets of HPS will be around for decades more until the supply of replacement lamps dries up.
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