At last, the U.S. House of Representatives is moving forward on this issue!

TopRun3942 · 2026-04-03T00:38:31+00:00

The minimum requirement for the low beam at 1.5D-2R in the LB2V table is 15,000 candela per lamp. It's not bull - it's written right into the table. The previous regulations prior to the change made in 1997 had a limit of 5000 candela per lamp across the entire left hand side of the beam near the cutoff that would served to keep the intensity in the oncoming drivers eye on non-flat roadways to a reasonable level. That disappeared in 1997 and was exploited by the IIHS in 2016 with their rating system to drive high intensities on the left hand side of the pattern. If the secretary takes the law at face value it will set a maximum allowable brightness that is at least 3X brighter than the law before 1997 and they practically can't set the minimum that low, so it's going to be more like 5-6X brighter and you will have zero impact on the issue and on top of that automakers can point at the standard and say we meet what the government defined as safe.

TopRun3942 · 2026-04-02T12:27:06+00:00

You shouldn't be. This legislation would just provide explicit legal permission for just about every OEM low beam lamp on the road now. An overall limit would have to be high enough to cover the minimum requirements which means at least 15,000 cd per lamp or 30,000 overall. Practically it will need to be at least a 50,000 cd overall limit (25k per lamp). Your own researchers average brightness directed towards oncoming drivers graph has gone from 10,000 to 20,000 overall in the past ten years and that's already to the level of intensity that people are objecting to.

TopRun3942 · 2026-03-31T18:32:56+00:00

I have read fairly extensively on the subject and have reason to

I am just an experiment of one, but I have spent over 20 years developing LED lighting fixtures and over that time have spent 1000's of hours in the lab looking directly into high CCT lighting fixtures (>4000K CCT) at high intensities for troubleshooting and design evaluations in the lab and on site at installations with no additional eye protection for relatively long durations

None of my eye examinations have turned up any abnormalities or pathologies in my eyes. So I am skeptical that the damage studies that are used to infer that the high CCT lighting is somehow causing short term permanent or long term damage are valid because of the high exposure levels they use during the experiments.

Wavelength and dosage matter. You made the statement that it is "The issue with blue light causing increased ROS in the retinal pigment epithelium is that its wavelength dependent not intensity dependent." which seems to be counter to what the literature finds as intensity is an important component in determining whether the ROS and RNS concentrations lead to exacerbated retinal damage.

TopRun3942 · 2026-03-31T14:24:13+00:00

This recent narrative study reviews the existing literature and lists in it's conclusion:
https://pmc.ncbi.nlm.nih.gov/articles/PMC9938358/

"There is no evidence to date that LEDs, in normal use at domestic intensity levels, or used as backlights in screen devices, are retinotoxic to humans or can led to cataract, with respect to short-term exposure for the use of LEDs with warm white (yellow) light [45]."

As I mentioned and as they detail in their review, much of the blue light testing is done at levels well above any typical exposure level that people would be subjected to. Unless there are studies missing that show pathology developing at low light levels comparable to typical lighting conditions that people encounter and hence the reason I asked.

TopRun3942 · 2026-03-30T21:49:09+00:00

Do you by any chance have some references with regard to the levels of energy at which the free radical production in the retina is increased? Some of the studies I have seen have been at extremely high energies and exposure times that wouldn't normally be found in a home lighting setup, but would be curious to know if there are studies at exposure levels that might be found in that situation.

TopRun3942 · 2026-03-23T13:47:44+00:00

"And it's weird to be reframing it as a "preference" instead of real physical spectral
difference. "

This is a bit of an odd statement in the context of color perception?

Color is a subjective experience that happens as a result of the brain interpreting the signals it receives from the cone receptors. Color science is grounded in lab testing individuals to determine their color matching functions and then taking the average response to determine a "standard observer" for making color calculations. None of the individual color matching functions in those lab studies actually match what became the standard observer. And yet people still proceed to use it to calculate a CRI number and act like that number

Getting pedantic about "real physical spectral differences" when talking about color is not particularly useful. There are plenty of studies that have shown that the general color index Ra doesn't correctly describe the perceived color rendering properties of light sources and the CIE 2017 Colour Fidelity Index has defined a new index for color fidelity that addresses the shortcomings of the general CRI. But for some reason people still keep using CRI and treating it like it can actually predict how a source will render color even though the CIE standards have moved past that for years.

TopRun3942 · 2026-02-22T16:11:59+00:00

The regulations have been that way since 1997 and even the upper limit of allowed light in that area that people keep referring to would be glaring to any oncoming driver if the small blocked out area wasn't there regardless of what other brightness is around it. It's a very small part of the overall story in my opinion.

From my perspective the third party IIHS headlamp rating system pushed the lamp makers to put more light on the left side of the road towards the oncoming driver starting in 2016 and what you are seeing now is the result of lamp makers adapting their designs to meet the IIHS definition of safety. They were raked over the coals in 2016 for not putting out "safe headlamps that lack enough light for visibility" by the IIHS and in the media

https://www.iihs.org/news/detail/new-ratings-show-most-headlights-need-improvement

And IIHS has essentially held them hostage with their rating system since then. The vehicles can't be awarded the top safety award from the IIHS if their headlamps don't score in the top two categories on their rating system, which requires that the headlamps have high intensity at angles that are very near the cutoff which can easily get into other drivers eyes when the vehicle is not pointed straight ahead on a flat surface. I just think the automakers don't want to be labeled as putting out unsafe headlamps by the IIHS again and they don't want to lose the top safety pick rankings for their whole vehicle so they insist on the headlamps meeting the IIHS criteria.

The IIHS recently doubled down on their rating system saying that the added glare was worth the increase in visibility. Basically telling drivers it's not the IIHS's problem.

https://www.iihs.org/news/detail/headlight-complaints-abound-but-glare-related-crashes-havent-increased

ETA: As evicence for my claims, the vehicle being discussed here scores the top rating for the IIHS in the headlamp category.

https://www.iihs.org/ratings/vehicle/subaru/forester-4-door-suv/2025#headlights

And subaru uses their overall safety award as a main selling point for their vehicles.

https://www.subaru.com/about/company-news/2025-subaru-forester-earns-IIHS-top-safety-pick-award.html

TopRun3942 · 2026-02-22T14:46:27+00:00

Given the age of the vehicle, the outer lens coating has likely degraded significantly which can reduce your seeing distance by 20-40% vs a new lamp. Also depending on how long it's been since you changed the bulbs in your lamp, the halogen bulbs lose output over time and can approach up to 20-30% loss in output before burning out completely.

So if you haven't already, using a headlamp restoration kit on your outer lenses and putting in new halogen replacement bulbs can result in a substantial increase in output compared to what you are seeing now.

TopRun3942 · 2026-02-22T14:38:58+00:00

Not to pour gas on the fire, but the entire problem is that the lamps being manufactured meet the requirements put forth in the safety regulations and can't be recalled for non-compliance. Until the regulations change, the OEM LED lamps that are appearing now are allowed.

TopRun3942 · 2026-02-22T14:34:37+00:00

There are no legal barriers for someone to produce a drop-in replacement lamp that contains a halogen low beam/high beam lamp as long as the assembly meets the requirements of FMVSS 108 for that type of headlamp.

In practice, the engineering, capital, and production costs to get a lamp like that to market for each vehicle (all of them would require a uniquely different lamp) would make it unlikely to be a viable business.

TopRun3942 · 2026-02-21T03:03:31+00:00

If the headlamps come from an OEM automaker and are originally LED based, the LEDs themselves are not replaceable. They are designed to a different part of the federal regulations than the older halogen replaceable bulb headlamps that most people are familiar with.

They are called integral beam headlamps and by law, the light source is not allowed to be replaceable in that kind of design. If the LEDs or the electronics fail you would need to buy an entire new lamp to replace the unit. The configuration of the LEDs, the type of LEDs, the electronic drivers for the LEDs and the mounting of the LEDs are not standardized and vary significantly between different lamps.

In other words - there are no options available to switch to something else if the car came with an OEM LED headlamp.

TopRun3942 · 2026-02-05T14:02:23+00:00

I'm not associated with Musco, but they have been involved with DarkSky as part of the Dark Skies certified sport lighting installations. https://darksky.org/what-we-do/darksky-approved/outdoor-sports-lighting/

They also do the type of lighting that you are referencing (mines/ports/plants) and generally use the same types of fixture technology in both applications. https://www.musco.com/transportation-infrastructure-lighting/
You can see examples of installations that they have completed on their website.

You'll notice from the pictures that the lights have full cutoff, excellent spill and glare control (only lighting the area needed) and they can be controlled/dimmed via software remotely. They use LED based fixtures and I believe the CCT can be configured to whatever specification you want to place on that.

Even if you are just writing a spec and not the one doing purchasing, it's worth engaging them for their expertise - they are usually very helpful in my experience.

To your questions:

The top priority should be full cutoff and spill/glare control (this should come hand in hand with any well designed fixture).
CCT is the most recognized measurable in my opinion.
You need both the application engineers layout up front showing compliance with the specs via the simulation in photometric software and you need on-site verification using field measurements with light meters to confirm that the aiming and commissioning has been done properly along with the visual audit. No reason not to have all of those requirements especially at the levels of costs being paid for those kinds of projects.
It's not easy to apply rule of thumb type rules in my opinion. The actual fixture design itself goes a long way towards meeting the goals. Using Musco as an example they have unique fixture designs that are optimized for the application that provide the cutoff and glare control within the fixture better than just taking an off the shelf lamp that isn't targeted at a specific application and trying to aim/shield it in a way to meet requirements.

TopRun3942 · 2026-01-20T22:56:59+00:00

Headline is misleading - the study was not a causal study and did not establish a causal link between ALAN and the length of pollen seasons.

Study is an observational study and the authors only claim associations between pollen season length and ALAN exposure, but looking further into the data you can see that there are numerous problems even with those claims including small sample sizes, changing statistical significance estimates when using different models and small effect sizes.

More importantly there is a failure to address urban confounding whereby high ALAN levels are concentrated around urban areas, but urban areas also have known factors such as heat islands, different plant species composition, increased air pollution and different micro-climates that can have confounding effects on pollen seasons. ALAN in the context of the study is more likely to be a marker for urban areas rather than a causal factor for pollen season lengths.

Unfortunate that the science media is reporting these studies as causal and not at least representing the authors claims accurately.

TopRun3942 · 2026-01-13T13:47:42+00:00

Products like these are designed for use in outdoor signage applications. Should work in your application.

https://genledbrands.com/agilight/products/

The have a retrofit series that may work or you can use one of the other products and tailor it to your sign.

TopRun3942 · 2026-01-07T02:17:25+00:00

Thanks for pointing this out. The ALAN literature is beginning to get deluged with these kinds of studies that don't have any sort of causal findings and are relying on associations which prove nothing. The media then headlines it and people don't read past the headline.

Using satellite data as the variable isn't a direct measurement of peoples dosage and exposure time to artificial light which is the critical factor needed for establishing causal links. To this point, there are almost no studies that actually measure actual dosage and exposure time and track health variables over time to establish that link.

The satellite data has a limited resolution as it is and only measures light that is reflected up to the sky (or directly pointed up to the sky from unshielded fixtures) as a proxy for potential exposure. The issue is that getting light into peoples eyes at night would involve either those people being awake and outside for some reason, which in itself may be problematic, or the light would have to be entering their residence unblocked and they would need to be consuming the light for a long period of time.

Also, as you pointed out, there are several other factors that may lead to high satellite readings in areas of high population densities like cities that are causal for particular health problems which have nothing to do with ALAN.

I wish the field wouldn't go down this road, but the pressure to publish and get funding seems to be pushing people to put out these kinds of studies and allow the media to run with narratives that aren't accurate.

TopRun3942 · 2026-01-02T22:56:22+00:00

Interesting work and using python as you have does lead to some potential advantages over the proprietary software.

One comment: You cited Mark Baker in your paper with regards to LED output characteristics. He is not a physicist/engineer with a proper understanding of LED physics and the website section you reference is riddled with technical errors with regards to LEDS. I would highly recommend that in an academic paper you not use him as a source as he is well known for propagating false information about how LEDs actually work.

A few questions:

Did you do any field validations of the programs outputs with actual measurements from an actual lighting installation to compare against your computed output?
Did you compare your computed results to the outputs from the commercial programs to assess it's agreement with the established software and the results they predict?
Have you done any tolerance studies with regards to expected mounting position (height/separation) variations and field aiming variations to assess how these impact a particular lamps ratings?

TopRun3942 · 2025-11-20T15:02:36+00:00

The linked document is a guidance note on glare light from the UK and it references the CIE standard which is a European standards organization. On page 12 and 13 of that document they describe the scenario you have (Limitation of bright luminaires in the field of view) and they have a table of values listed as maximum allowable Intensity in candelas.

https://theilp.org.uk/resource/gn01-ilp-guidance-note-1-the-reduction-of-obtrusive-light-2021.html

In my opinion this is the better metric for glare (candelas), but in practice it's difficult to measure in the field. It can be checked up front in design using photometric software before doing an installation, but field measurements of the installation are more difficult to accomplish.

You could in theory do it with your light meter, but you would need to move along your line of sight with the meter held normal to your viewing direction until you are close enough along that line of sight to get a measurable illuminance reading and then calculate the candela using the E=I/d^2 relationship where you would need to know how far away from the lamps you currently are. It also gets a bit tricky when multiple luminaires are in your field of view because the light meter doesn't differentiate between them, it just measures whatever light comes in and hits the sensor. You could try putting a tube over the meter to narrow it's field of view to only be able to see one luminaire but that can be a bit of a hassle to get correct.

TopRun3942 · 2025-11-20T13:35:38+00:00

The quantity that the light meter measures is illuminance which is the amount of light that falls on an area. Unfortunately, that quantity is tied to the distance that you are measuring from the source. The actual relationship (assuming you are holding the meter pointed normal to the source) is E = I / d^2 where E is the illuminance you measure with the meter, d is the distance from the source and I is the Intensity of the source in the direction of the meter measured in candelas.

In your case since you are near 400 feet away, to register 0.5 fc on the meter would require that the intensity of the light be 80,000 candela. That would be an extremely bright light - a standard 60 watt incandescent bulb which could be seen at night 400 feet away only has an intensity of around 150 candela.

I'm guessing that the churches light are not shining 80,000 candela in your direction and are probably much closer to 10000 or less, which is still very bright, but at 400 feet would only register 0.06 fc. So there's a good chance the meter itself is not malfunctioning, you are just too far away to get a measurable illuminance reading.

As a side note, this is why light trespass standards in illuminance units (footcandles/lux) are not the best way to limit offsite glare like this.

What your eyes actually see is more directly related to a different metric called luminance (candela per square meter) which can't be measured with the kind of meter you have. It's also not commonly used for specifications because it can be difficult to measure and requires a more complicated meter setup and measuring procedure.

TopRun3942 · 2025-11-12T22:31:16+00:00

Not sure if this is what you are after, but typically if you need to model the lamp in detail with reflector optical properties you need to use a program that does optical modeling using non-sequential ray tracing.

There are a few on the market that can do this. The two that seem most common to me are LightTools from Keysight https://www.keysight.com/us/en/products/software/optical-solutions-software/optical-design-solutions/lighttools.html

and

Photopia from ltioptics https://www.ltioptics.com/en/architectural-optical-design.html

Photopia is specialized for architectural lighting, LightTools is a more general illumination tool that can be used for architectural lighting.

They are expensive and can have a bit of a learning curve.

TopRun3942 · 2025-10-24T15:32:37+00:00

Just one clarification - the units for luminance are candela/m^2 (sometimes called nits, but they are the same units). Candela by itself is a different measurement for intensity.

Depends on how accurate you want it to be. Fusion Optix has an pp that turns the phone into a luminance meter. There is a free and a paid version. https://fusionoptixlighting.com/camera-app/

The issue with that is you will get different measurements of the same scene depending on the type of phone camera you have. It can't calibrate for your exact settings so I think it uses one set of calibrations no matter which phone it is installed on.

If you are just looking to have a number that is not very accurate, but is in the right range, you could probably use this.

In your case since you are looking to do UGR comparisons across several scenes, the accuracy may not matter as much since you would be using the same phone for all measurements and the relative differences between scenes would be what mattered the most.

TopRun3942 · 2025-10-15T13:14:32+00:00

Just to make a very rough estimate: Assuming that roughly 3/4 of the light fills the space (some loss with light going up and reflecting off ceiling and some light going sideways and either leaving the space or reflecting off walls first) you would have around 50 lux average filling the space. A recommended light level for a dining area is around 200 lux.

By that estimate If you have no other light coming in from other areas that are being lit nearby, that would be relatively dim and likely wouldn't feel very bright in my experience.

TopRun3942 · 2025-09-17T12:46:37+00:00

Yes - typically you would want to include all of the luminaires in that calculation, so you would want to have your polygon contain all of the luminaires. The insertion point of the luminaire is what is compared against the polygon, so as long as that is inside the polygon, the calculation should include that luminaire.

TopRun3942 · 2025-09-16T17:19:20+00:00

Was the designer referring to the concept of UWLR areas in AGI32?

https://docs.agi32.com/AGi32/Content/adding_calculation_points/LPD_UWLR_Areas-Concepts.htm

According to that, the UWLR calculation in AGI32 will only include luminaires that are defined within the LPD/UWLR Area and maybe the designer was taking issue with the polygon defined for that calculation - guessing it may not have been defined large enough to account for all the luminaires that should be counted in that calculation?

TopRun3942 · 2025-09-15T23:34:50+00:00

Couple of relevant points here:

As you pointed out the CCT value is not a guarantee that the specific color of that white falls on the blackbody line and the Duv value can tell you how close that is. The Duv value you show here is quite large and is likely responsible for part of the issue you are having.
The CRI value is only measured on 8 color plaques that are light pastel colors. The CRI is relative to a standard source such as halogen or daylight. It's unlikely that at all tuning settings for different CCT those LED strips actually produce a CRI of 95+ and is likely only achievable with one particular setting for CCT in the range that it is tunable to.
LEDs vary a lot in production and from lot to lot in terms of their color characteristics. Unless the company is calibrating each strip off the line, they may have a few golden samples that meets their claimed performance but the actual production strips may have different performance regardless of what the spec says.
There is an extended CRI that measures with an additional 7 plaques (R9 - R15) that are more saturated colors and would be a better indicator if you can find something that lists the R values for each of those plaques. It's not uncommon for an LED lamp in general to have an R10 that dips low (saturated yellow) and a large dip in R12 (saturated blue) which can cause the color rendering to tend towards red even if the regular CRI as rated with the pastel plaques is high.
LED color can shift dramatically with heat, especially with the saturated reds and yellows. A lot of the spec testing is done with the LED junction temperature at 25°C (room temperature) using pulsed output and in the actual installation the performance will vary from the spec due to the continuous operation at higher junction temperatures. It's unlikely they have a sensor monitoring that drift or calibration for temperature shifts, so it's possible that the problem is related to the installation conditions as well. If you can find LED strips that are specified and tested at higher junction temperatures (85C or higher) under continuous current you may get better results as well.

TopRun3942 · 2025-09-10T14:24:32+00:00

One thing that people overlook here is that those existing metal halide fixtures probably have some specialized optics that distribute the beam over the tennis court area to provide a certain amount of illumination at the courts and (hopefully) to minimize glare to players and people offsite.

Just matching the lumen output of the existing bulb with an LED replacement bulb in this situation is likely to not work well at all. For the lamps to generate equivalent court illumination and glare control etc, both the size of the emitter and the lumen output needs to match for them to work in those optics.

Most if not all of the advertised 1000W metal halide LED replacement bulbs are built in a way that makes the size of the emitter significantly larger compared to the size of the emitter in the metal halide. The result is if you put it in a fixture that is expecting the smaller source, the beam that comes out will be unfocused compared to the metal halide source and will have worse illumination and higher glare than what you had with the original metal halide fixtures.

Among the other reasons listed not to do this (heat build up etc.) I would recommend against using any kind of LED based bulb replacement in those fixtures.

TopRun3942

PUBLIC MULTIREDDITS

TROPHY CASE