Decided to start a second thread because I’m asking a slightly different question.
The city next to me is experimenting with reducing actual light levels with new LED fixtures
Their allegation is “the streets don’t need to be as bright because there’s less glare and the light quality is better”
A city commissioner and bicycle / pedestrian advocate I know mentioned this to me because I’m kind of a lighting / bulb geek, and I agree with him this doesn’t pass the smell test. The fixtures they are testing can be driven at different levels, and/or they’re selecting a smaller, cheaper fixture. So either it’s an engineer with a batshit crazy idea or they’re trying to cheap out.
I know that the actual lumens for an LED fixture can be less, due to better light and improved optics.
When a manufacture says "this fixture is an equivalent to XXX watt HPS, don’t they already factor in light quality (although maybe they assume full-cutoff HPS fixtures, and these are semi-cutoff).
Should the actual light levels on the surface of the street be the same for an equivalent figure? I measured the light of the LEDs to be about 40% less.
Human eyes are funny things, and the way they perceive light is complex. Simple lumen measurement won’t get you a directly compatible answer comparing light sources with diverse spectral output characteristics. Light sources that are strong line spectra seem to never work as well as sources with wider spectra. The poor colour reproduction reduces apparent contrast and can significantly skew perception of colour. The worst offenders are sodium lights, but mercury is not good either.
It isn’t unreasonable to suggest that “good quality light” - as in light with better colour rendition - will result in greater visual contrast and generally easier seeing than the usual street lights, and lumen for lumen, the better CRI source may produce lighting that has noticeably superior clarity. So reducing the total lumen value may be quite reasonable.
Nope. There are no standards (at least have not been any) and manufacturers have seemingly chosen the measurement that makes their product look best. The debarcle with CFL lamps is a good example. No CFL lamp ever seemed to be visually anything like as bright as the manufactures claimed they were as an incandescent equivalent. LEDs seems curiously to the be visually better.
I really do not understand LED lights.
I have had LED flash lights. For short distances they were great nice and bright. But if you use many of them the light does not carry very far. If you are outside and want to light something up very far away to check it out it just does not work, if you want to light up the path just in front of your feet they are great. I feel like duh what is going on.
I live in San Jose CA. They had replaced street lights with the yellow dim lights because of Mount Hamilton. The old street lights were reflecting too much light into the sky making it harder to make observations from Mount Hamilton. So they went to the low intensity yellow lights.
A few year ago they began to change the lights out to bright white LED street lights. It is so nice to not live in a city neighborhood with dark streets. The LED lights do not reflect into the sky.
Also another thing I remodeled a bathroom and added two LED down lights. When working in the bathroom with the lights on they seamed to heat up the room. Enough so the tile contractor worked in there this summer with the lights off because of the heat. I do not see how LED lights can transmit heat.
Light is light.
The distance the light “throws” is independent of what device is generating it - it is a function of how well collimated (focused) it is. Cheap LED flashlights don’t use a reflector, so they tend to have a wide beam, with poor “throw.” Better flashlights use a parabolic reflector or even a lens to greatly increase the distance. LED streetlights have optics designed to direct the light to exactly where it is needed. Unlike traditional streetlights, which tend to spill light in a circular pattern, LED lights can be made to throw light in a very wide, rectangular pattern. LED optics are now good enough that they are being used for Stadium lighting. I’ve recently been involved with two LED stadium jobs. At one of them, the parks guy said they they used to get complaints from the neighbors all the time if the lights stayed on late (due to light spill). Now, with LEDs, the neighbors can’t even tell the the lights are on…
They are starting to make their way in to video shoots. My son was telling me of a 5K Fornal like light. Small battery pack that last for 8 hours. no more stringing out cords every where and renting large generators.
You probably just experienced crappy LEDs. The good ones can certainly carry very far. This is not a function of the lighting tech, just the brightness and lens/reflector. And LEDs excel at lumens/watt, so technically they should carry further than many other bulb types at the brightness levels you’d use in a flashlight or bike light (<= 1000 lumens). The better ones either come pre-set to a long-range focus, or have an adjustable slide that changes from floody (broad, wide light) to spot (focused into a narrow beam).
I’ve just tossed all my old bulbs (a motley mixture) and replaced them with 7W GLS LED bulbs. The light they generate is absolutely fine. They should pay for themselves within 6 months. It also means I only have to carry one type of spare.
Old streetlights have poor shielding and poor optics. Much of the light is spilled to the side and above. This means some of the excess light goes directly into the drivers’ eyes - i.e. glare. Which makes it harder for the drivers to see the road surface.
If the new streetlights have good shielding and good optics (all the light is directed down onto the road surface), the lack of glare means you don’t need as much illumination to see the road surface.
I first used them in flashlights. I worked as a stationary engineer. In trouble shooting AC problems in tenant spaces I would have to check vav boxes in the ceiling above the ceiling tile. If I was checking out something close most LED lights were great. But if I wanted to look across the ceiling the light from many LED flash lights did not carry far until it faded out.
The one exception is a Mag light. I managed to find on sell a combo set. That is two flashlights one using AAA batteries and the other D batteries for around $23. But when the bulb quit in the three cell D flash light the replacement bulbs that I could find were in the $19 range.
All the LED bulbs I have at home have multiple diodes giving off light. Seems like it would be harder to focus a diffuse source like that rather than a single point like an incandescent filament. Do flashlight bulbs (which are obviously smaller) use just a single diode, and can they match the output of incandescent?
It should be just about lumens output. It should be about color, too.
When the mercury vapor lights were replaced with sodium lamps, the color spectrum changed. As someone who is red/green colorblind, I prefer driving down a street with mercury vapor lights or no lights at all. The sodium lamps output is noticeably darker to me because of the limited color spectrum.
There is no single answer.
LED sports lighting uses arrays of individual LEDs, each with their own lens.
LED flashlights can use a single high-output LED (like the (potentially) 30W SST-90 chip), which can be focused with a parabolic reflector. Other flashlights use an array of high-output LEDs, each with their own reflector.
The brightest LED flashlights are now brighter than all but the most absurd incandescent ones (I’m talking the 100W halogen flashlights that are advertised as being able to set things on fire).
We are very lucky here, the village council installed new LED streetlights a few years back, they are powerful in a discreet way — I think 14 arrayed reset bulbs — and most important of all pure white.
The previous ones were white but with a dingy step in the yellow spectrum of the olden time, like candle light, not though the dreaded golden glow of incandescent house bulbs. And still less those hellish horrors of amber or orange thrown up by Sodium.
I think you mean Fresnel light. It’s pronounced fer-nal (from the French physicist who invented it).
It’s actually a type of lens, typically looking like a bulls-eye pattern from the front. The main advantage is that it takes much less glass to make than a full lens with the same optical properties. First used in lighthouses.
In stage & film lighting, it’s common for workers to refer to a ‘Fresnel light’, meaning any light using this type of lens. They are used for general, overall, more diffuse light, as opposed to a tight spotlight.
Yes, a point source is definitely easier to focus than an array or an extended source. But they now make very powerful emitters, some as bright as a 100-watt bulb.
As for flashlights, it depends on the design. Flashlights designed to produce a tightly focused spot (like a spotlight) generally use one very bright emitter - or sometimes a few, each with its own lens/mirror. Flashlights designed to illuminate a large area (more like a lantern) generally have multiple LEDs without optics. Some have both, so you can switch between the two modes.
That sounds odd to me, my french is poor but not THAT bad. Wiki agrees with me. FRAY-nel
The sad part is I still remember the university optics lecture where I first learned about the Fresnel lens 100 years ago. I’ve been pronouncing it FREZZ-nel like a stupid mook the whole time.