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Friday, 07 February 2014


Back to nice lights, at night!
Photography in similar situations hould be most interesting.

Despite the monochrome orange output of sodium vapor lamps, scenes illuminated by that source are easy to color-correct. Also, our pupils are less sensitive to the red side of the visible light spectrum. The result is our pupils do not contract as much, thus allowing more photons to reach our retinas—an advantage for night driving. Also, it is no surprise streetlights and roadway signs are designed to maximize contrast. I remember the transition from mercury vapor to sodium lights in Omaha during the 1970s. At the time, many environmentalists raised havoc about sodium lights harming trees. The reasoning being that sodium lights did not allow trees to 'go to sleep' at night.

Well, unless you shoot b&w.

Comparing the left and right photos, you might think the LEDs will reduce light pollution. Unfortunately (more so for astrophotographers) it seems the opposite is true:


I do a great deal of night photography, particularly in an historic SF Bay Area ship yard. One of the initial frustrations but eventual great pleasures of shooting here has been the wildly divergent light sources. In one scene I might have color from sodium vapor lamps, fluorescent lights, tungsten, LED, moonlight, and the glow in the sky from nearby cities. It was from this experience that I "got" the fact that night photography is as far from photographing "what is" as one can imagine, and that it is instead about seeing what the camera sees and then exploring where that can take you. I love crazy lighting that cannot possibly be "balanced."

And then, a year ago, I began to notice that the colorful older lights were being replaced with LED lights. I cannot quarrel with the need for energy efficiency, but I was very disappointed to see that the overall effect is much like shooting in daylight - not at all what I have in mind when shooting "on the dark side."

The wide-spectrum LEDs will vastly increase light pollution, blocking viewing of most of the stars and other interesting deep-sky objects. Bah!

Dear Mike,

The Gizmodo article was appropriately light in tone regarding photography, seeing as this is really a champagne problem. Over the span of modern color photography and cinematography, we've seen streetlamps move from incandescent through fluorescent, mercury vapor, high-pressure sodium, and low-pressure sodium. The look has always changed. Yeah, it's a technical problem if you're trying to do an historical period piece with a real scenery. So what else is new?

A real problem that does arise with these is that it's making life worse for real astronomy. As in the science, not just taking pretty pictures. Major famous observatories, like the Hale 200 inch telescope on Mount Palomar are having serious problems due to light pollution. Convincing municipalities to go to low-pressure sodium, with better down-pointing reflectors, helped. The narrow-line emission could be filtered out (said narrow-line emission also made it impossible to color-correct photographs made under low-pressure lights, in contrast to high-pressure sodium), minimizing the impact.

The problems with the LED lights are that they are broad-spectrum. You can't filter them out and, because they are closer to daylight balance, they have a lot more blue in their output. Short wavelengths are what the sky scatters most effectively, so the light pollution problem and the size of the light domes increases all out of proportion to the amount of light.

In addition, because LEDs are substantially more efficient, many municipalities are using them to increase the brightness of their streetlights without increasing power consumption. That's totally understandable from a practical point of view; brighter streets reduce crime, make people more comfortable, and encourage evening commerce and traffic. In terms of quality of life, they are an understandable win, on the whole. But for scientific astronomy, many previously-prime sites on earth are increasingly becoming unusable.

pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
-- Ctein's Online Gallery http://ctein.com 
-- Digital Restorations http://photo-repair.com 

> In terms of quality of life, they are an understandable win, on the whole.

Not so much. Night lights, especially blue frequencies, interfere with biology. It further reduces urban biodiversity since so many organisms (not just animals, but plants and many micro critters too) are dependent on dark/light cycles for navigation, {evading} predation, telling what time of day and year it is, and more. Night lights can harm human health directly because humans too are organisms, and dependent on light/dark cycles for keeping our clocks, and other bits of physiology such as the immune system, functioning.

It doesn't really help with crime either. The brighter lights just make the shadows darker, and even at walking pace my eyes can't adapt to the sudden changes between being in the light and being in a tree shadow. This puts me much more at risk from a bad guy (or a bad driver) than the old dim lights that didn't interfere so much with dark adaptation. Most criminals aren't deterred by steady lighting in any case--motion detection lights are far more effective.

LEDs are the bane of our urban futures. Ctein got it exactly right-LEDs should be used to cut our power consumption, but instead they're being used to amp up the illumination. I haven't encountered any LED streetlights yet, but every week I spot several new LED billboards around Denver. Each of them are many times brighter and more conspicuous than the conventional signs they replaced.

One was placed right beside the road, at ground level. The message had a white background, and was turned up as bright as airplane landing lights. As part of my complaint to the city code department, I photographed it with a bracket of settings. The street scene looked normal, like my eye would see it, at 1/30/f3.5, ISO200. This left the LED sign totally burned out, overexposed and iillegible. To render the sign with an off-white background, clearly legible, I had to stop down to 1/125/f11. That would indicate that the sign was 4 1/2 stops too bright for the surrounding scene. In the image stopped down for the bright sign, you could no longer see the sidewalk and the gas station in the background, and the headlights of a passing car were faint. The human eye is even less capable of dealing with this brightness difference than a camera. It can take us minutes to regain our sensitivity to dim light. This is a safety issue, as well as an issue of good taste.

The city found that the sign contractor had turned on the sign and left it on maximum brightness, without properly calibrating it. It's slightly more acceptable now, but there are others like it that can cast shadows a thousand feet away. There seems to be almost no local or national resistance to this invasion of our nighttime roadway landscape.

I do care about astronomy, but this intrudes on everybody's daily, er, nightly life. C'mon, its supposed to be dark at night!

This has made it strange and difficult (at least for now) to shoot at night. Never quite sure how to deal with the mixed lighting.

I echo Ctein's comments. As a former astronomer who chose our current location because I could see the Milky Way, I regret this move, however energy conscious it may be. The International Dark-Sky Association agrees: http://www.ledsmagazine.com/articles/2009/10/dark-sky-says-boo-to-blue-light.html

I can't stand strong tungsten colors, so any cooler artificial light sounds great to me.

For those interested in reading about artificial illumination and it's impact on our world, I recommend Paul Bogard's "The End of Night". It's a really thought-provoking read.

The wide-spectrum LEDs will vastly increase light pollution

That's strange. We are having LED lights installed here and the general concensus is that they will reduvce light pollution.

They certainly seem to put most of their light down towards the road, unlike the olde sodium lights which you can see from miles away.

A point people miss about light pollution is that the narrower the spectral range of emission from a light source, the easier it is for astronomers (and other light-sensitive organisms) to deal with. That's because narrow bands of the spectrum can be filtered out of the background sky glow with high efficiency, rendering the sky effectively dark. Thus the push for narrow-band low-pressure sodium lamps near observatories, and high-pressure as second best. Also, narrow spectral bands are less likely to fall within any one plant or critter's critical sensitivity range in the first place, leading to fewer disruptions of photosensitive biological pathways and ecological systems.

LEDs will illuminate the sky, even indirectly by reflection from the ground, with the entire visible spectrum, so the perceived amount of light scattered from the air could be quite high compared to locations with LPS lighting, and any organisms with light sensitivity in the broad LED output band could be affected. Yellow sodium night lights are at least a little reminiscent of firelight - we've had plenty of time to adapt to that. I'm not sure how much LPS and HPS lamps depend on rare-earth elements, if any. The scarcity of REEs could be either an economic consideration or an illegitimate excuse for LED use. Of course, LED night lights could also prove a boon to pharmaceutical sales.

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