Quote:
Originally Posted by Camelopardalis
I could be wrong my local lights might be normal ones, but they're definitely white and they're fairly directional...doesn't mean they're LED I suppose, but with all of Sydney's light pollution I'm not sure it'd make much difference 
I know LEDs are quite popular for their energy efficiency in some places. |
Road lights and industrial floodlights etc (which are the main source of general light pollution) are still pretty well all sodium or mercury these days, but you do see other technologies in areas where lower illumination levels are acceptable (parks, cycle paths, etc), including fluorescent tubes, CFLs , LEDs , etc.
High-pressure sodium lights give a yellowish white light, while high pressure mercury lights look white at first sight, but actually have a strong green cast. Because both are emission sources, they have a narrow band emission spectrum, so are responsive to light pollution filters.
LEDs are starting to be used in industrial lighting applications. They cost quite a bit more than the mercury and sodium lights that they replace, but have much longer lifetime between replacement, and much lower energy costs, so are cheaper over their lifetime, despite their higher installation cost. They are also designed to point much more accurately than the older light fittings, so can generate a lot less light spill / pollution. I would expect to see them make their way into public spaces over the coming years, but it will probably be a couple of decades before the transition is complete, because they are still not a viable option for the high-mast lights that you see at major intersections, sports stadiums, etc.