Future of Light Pollution Reduction Filter

[Akira]

I bumped into an article on the environmental risk caused by the ever increasing LED lighting.

https://www.science.org/doi/10.1126/sciadv.abl6891

That made me think about the light pollution reduction filters.  I've been dreaming of shooting the nightscapes of Tokyo with the starry sky, but the excessive light pollution has make it difficult or nearly impossible.

There are a bunch light pollution filters in two different types offered by various brands: the ones use special colored glasses and the others use glasses  with the interference coating.  The former can be used withe wideangle lenses, but the reduction of the two bright mercury spectra is not efficient.  The transmission character of the latter is much better calibrated to eliminate all bright spectra of both mercury and sodium lamps, but it cannot be used with wideangle lenses, because the transmission curve will be shifted when the angle of incident light is more oblique than about 17 degree.

So far as I understand, white bright LEDs combines the near-UV blue/purple light and the yellow light stimulated by the near-UV light to make the emitted light appear white.  I suspect that eliminating this near-UV light should be easy: you can just use something like a Skylight filter.

So, would it be easier to eliminate the light pollution in the (very) near future with the replacement of the mercury and sodium lamps with the white LEDs?  Is it too much of wishful thinking?

[Gone]

Or just turn off those lights and save wasting energy!

[Akira]

Or just turn off those lights and save wasting energy!

That can be ideal.  But the "nightscape of Tokyo" will turn out pitch black!   

[Akira]

Ooops...I thought I started this thread in the "Camera Talk" section...sorry...

[Øivind Tøien]

White LED spectra are quite wide, no there is no single narrow peak as in the sodium vapor lamp spectra. I think the consensus is that it is much harder to filter out as the filter will also remove the wavelengths of interest in the night sky object. In general  it is problematic to obtain a natural white balance with these filters. Some popular filters like L-enhance ( https://www.astrofilters.com/2021/12/27/optolong-l-enhance-2/ ) are letting though the very narrow bands for hydrogen alpha and oxygen emissions.

I see a very clear trend here locally during the last 6-7 years I have been active with astrophoto; light pollution has gone from sodium orange to white, and become worse. The best was the fall they changed lights on the nearby main roads and they had it all turned off during the construction work. I found it interesting that the article found that the LED lights caused power consumption to increase, as the higher efficiency was canceled by the trend to increase light output. One could hope that there will be some more thinking around light pollution spurred by the high power costs these days, as happens in some cities.

[Gone]

I have noticed, while flying at night, that the new led lights, while better shaded from above, cause much more light to be reflected from the ground. I live on the outskirts of a large town and apart from the moon, planets and a few of the brightest stars we see nothing in the sky at night except for an orange glow over the town centre.....

[Macro_Cosmos]

Interference filters are far better in terms of colour rendition and optical density.  It is worth forgoing an ultrawide angle lens to be able to use them.
Correct -- they do not work with LED light at all.

The light pollution filters work very well in older cities such as Sydney.  I used one and saw a clear improvement in colour that was hard to replicate in post-processing.  In newer or rapidly growing cities who adopt LEDs, not so much.  I tried them in China (Beijing, Shanghai, Suzhou), it has no effect. 

I suspect that eliminating this near-UV light should be easy: you can just use something like a Skylight filter.

Unfortunately, this is wishful thinking in my opinion.  LEDs are not all the same.  It would be impossible to create a filter that tailors to every single type of widely used "white light LED", let alone colourful ones used in billboard screens and advertisement.

Cheap white LEDs are strong in blue, how about better quality ones (higher CRI%, sunlight mimicking)?

[Akira]

Øivind, Chris and Daniel,

thank you for sharing your real world experiences, thoughts and knowledge.

I forgot about the huge billboards using LED.  Also, I remembered some high-CRI LEDs use RGB chips in one package.  So, the light pollution will be or have already been unmanageable...

[Ilkka Nissilä]

I think as the cost of electrical energy increases, probably also the night lighting will be adjusted or redesigned to minimize the power usage. However, there are safety aspects also that are pointed out; having some lights on the streets helps people see where they're going and maybe also reduces crime. I suspect the lighting can be significantly dimmed without causing problems.

As more and more energy production moves to wind and solar power, the availability of energy will fluctuate more as a function of time. It could be that a system can be devised which automatically or semiautomatically adjusts the night light usage based on how much energy is available. At night it used to be that electricity was cheaper but at least in my country this difference is typically now quite small, and this is probably because industry has adjusted its processes to use the night electricity more as it is less expensive.

Thus it may be that during some nights there will be less light pollution than during others. This could then be exploited by photographers.

[Hugh_3170]

Interesting thinking - the shape of things to come.  Thank you for this.

..............

Thus it may be that during some nights there will be less light pollution than during others. This could then be exploited by photographers.

[Gone]

The level of air pollution and cloud must also be factors - if the air were clear then there would be nothing for the light to illuminate and it would just pass out to space?

[ColinM]

Interesting topic Akira.

See my views on urban light pollution below.
But is there also reason to wonder how good an idea Elon Musk's Starlink Satellite project is?
And how he was ever allowed to proceed with this, without greater consensus from people outside big business?

How essential is it?
Check here if you just want to sign up

White LED spectra are quite wide, no there is no single narrow peak as in the sodium vapor lamp spectra.

I see a very clear trend here locally during the last 6-7 years I have been active with astrophoto; light pollution has gone from sodium orange to white, and become worse. ....I found it interesting that the article found that the LED lights caused power consumption to increase, as the higher efficiency was canceled by the trend to increase light output.

Two great points Øivind

1) Back in the 1980's I used to do a lot of B&W processing at home.
I upgraded my "old-school" red safelight for a brighter one that seemed to have a sodium tube in it.
To check this, I tried raising the blackout at night, so the streetlights could shine in.
That seemed to be almost as safe

2) The UK has been changing its streetlighting from Sodium to LED over the past 10 years.
The outcomes of this have been

• Light pollution is now lower as the light spread is much more downwards
• The old lights had a timeclock and in quiet residential areas would be turned off from around 00:30
  This allowed night photography if you stayed up
  When the LED lights went in, they left them on through the night... there was still some light leakage so overall, night photographers were worse off
• I understand the human eye responds to LED lights differently as we get older
  Hence many people find some newer car headlights really dazzling
  I found the LED streetlights seemed to give poorer illumination at night compared to the previous sodium ones

[Øivind Tøien]

Thanks Colin, and very nice story about using sodium streetlight as darkroom lighting.

Safety from streetlights have more to it than just making them as bright as possible. As some cities have found out, careful planning to avoid large variation in intensity of nearby areas is more important. An increase in brightness in one area could actually make the close not so bright areas less safe with no change in their light intensity. So if used carefully, LEDs can be a big improvement. Remote control of brightness and color temperature can really help, for instance making light warmer closer to bed time as on our computer and phone screens.

When crosscountry skiing at night in winter, I actually prefer a not so bright headlamp, as it allows me to use other light sources such as moonlight to view other things around me not reached by the headlamp, like a moose hiding in the brushes or a nice snow covered tree that "needs" to be photographed.

[Ilkka Nissilä]

Interesting topic Akira.

See my views on urban light pollution below.
But is there also reason to wonder how good an idea Elon Musk's Starlink Satellite project is?
And how he was ever allowed to proceed with this, without greater consensus from people outside big business?

I guess space is not very strongly regulated and each country can freely choose to use it. In the US, it seems that people who have enough money can do almost whatever they want.

Because of the increasing numbers of satellites I turned away from photographing the night sky.

I wonder if the increasing numbers of satellites will cause damage not only to scientific observation of space, but also our ability to detect asteroids that are on a collision course with Earth.

How essential is it?

For sure it is not essential at all, but wealthy people living in remote areas can get better internet access that way and Musk can fund SpaceX by selling subscriptions to Starlink.

• The old lights had a timeclock and in quiet residential areas would be turned off from around 00:30
  This allowed night photography if you stayed up
  When the LED lights went in, they left them on through the night...
  

I imagine that with the increased prices of electricity, the night lighting will eventually be turned off again.

I find it ironic that when there is a newer, more efficient technology available, people decide to use it to light streets all night whether they are needed or not, instead of taking the advantage of reduced energy consumption and the positive effects on our planet's environment.

[ColinM]

Sorry Akira, we're well off topic now, but briefly...

I prefer a not so bright headlamp, as it allows me to use other light sources such as moonlight 
to view other things around me not reached by the headlamp, like a moose hiding in the brushes

Some of you are dealing with problems I'd occasionally like to encounter....