There is nothing wrong with LED lights. There is just a big problem with cheap, poorly designed LEDs. You can use proper optics and control the light exceptionally well and put it exactly where its needed with very little spill over or reflections up. You can also chose whatever color and color rendering index (CRI) you like but all of this costs more money and municipal bean counters are drunk on the lowest bidder. So we get glare bomb blue light shows. I used to design this stuff so feel free to ask questions.
this post was submitted on 19 Jul 2023
144 points (91.4% liked)
Technology
59020 readers
2987 users here now
This is a most excellent place for technology news and articles.
Our Rules
- Follow the lemmy.world rules.
- Only tech related content.
- Be excellent to each another!
- Mod approved content bots can post up to 10 articles per day.
- Threads asking for personal tech support may be deleted.
- Politics threads may be removed.
- No memes allowed as posts, OK to post as comments.
- Only approved bots from the list below, to ask if your bot can be added please contact us.
- Check for duplicates before posting, duplicates may be removed
Approved Bots
founded 1 year ago
MODERATORS
So I’m a wedding photographer and in the past 3 years I have noticed an increased amount of the lights at venues strobe or have really bad banding when I set my shutter speed to higher than 120. My assumption is that the new LED lights are flickering at a consistent rate to save energy but at the cost of the photos I take. Is this the case? That cheaper LED lights will flicker like that?
The strobing is due to the way they're powered. When converting AC power to DC power, you can either convert the positive half of the AC sine wave (half rectified) or both positive and negative sides of the AC wave (full rectified). Cheap lights use half rectifiers so as the AC feeds in, the light is only getting powered half the time and off the other half of the time. This happens so rapidly that we don't really see it with our eyes, but with a camera it's very noticeable. AC cycles at 60 cycles per second (in the US), so it makes sense that you're seeing it at 120 shutter speed as this equates to 60fps.
I'd consider talking to some of these venues about it as I assume they're typically used for events that'll be filmed, so using shitty lighting is ruining it for everyone same as if they had the toilets sitting in the middle of the dance floor.
Add to that, the way they are damned is typically by flickering them off and on aka Pulse width modulation. This is super common in LED strips.
So LEDs are generally very bright by default, and there's a limit to how much you can really dim that. The solution used is often to flicker the LED at high speed, imperceptible to human eyes, called Pulse Width Modulation (PWM). Basically, by changing the percentage of time the LED is on (the width of the ON pulse) you change the perceived brightness off the light.
Cheap LED designs do this slower, cause the hardware and LEDs are cheaper. It's not really to save energy, but to adjust brightness and manage heat.
Also, probably more importantly, cheap LED bulb designs just don't deal with AC current as well, so you get the 60Hz flicker from the electrical line cause that doesn't get regulated out correctly when converting to DC.
You're seeing the 60Hz sinusoid caused by using AC electricity. 60 peaks, 60 troughs -- but the like is actually turning on and off 120 times per second when on AC, unless it's first converted to DC. Cheap LEDs just feed AC.
Not sure why, but the high power LEDs you see in cars do this if they're cheap or done poorly. Mine came with like an ant-flicker ballast or something.
So what I heard a long time ago is that all LED lights essentially strobe on and off constantly, faster than the human eye can detect, though i’m willing to bet the better ones are constructed in a way that you wouldn’t notice at all (whether with the naked eye, or through a high shutter speed camera, as you mentioned), but the shittier ones strobe more frequently and not at a rate that’s as smooth/consistent as the better ones. As a little anecdote, I bought a lower quality light-tablet for tracing a while back, and was getting crazy headaches after using it for maybe an hour or so. Had to stop using it, and I think it must be an example of what poor quality LEDs are like.
So LEDs can either be strobed or powered consistently with no blinking at all. It's a design choice and it depends on how you convert the power from AC to DC and how you want to control the brightness of the LED. It's cheaper to feed an LED power that is modulated/strobes so all the cheap vendors do that. You can also get away with strobing the LED to achieve a brightness assuming you do it at a very high frequency so our eyes don't perceive it. If you buy a quality LED light fixture there should be no strobing effect what so ever.
What was the greatest design challenge you faced?
This is not at all a LED problem. It is just very poor execution. When we switched to LED in our and neighboring cities the light pollution went down very noticably. The switch should be used to use light smarter, not just blast more with higher efficiency. We now have some streets that even have motion sensing and dim to 5% power when not in use.
Quick counter: lower kelvin lights are terrible for color reproduction. Pure sunlight is around 5000K, and has a CRI (color rendering index) of 100. Switching to warmer (lower kelvin) lights is going to also alter your CRI, and will change the way that you perceive colors. If you need high color discrimination, that's going to be bad.
For outdoor lights, in most cases that's not a problem.
Usually. In most cases, you aren't going to notice just how much the colors have shifted, because your brain automatically adjusts. Youre perception of color is usually how colors appear relative to other things; you will see a red as red because your brain is comparing it to other objects with a known color. OTOH, if you're taking photos under poor lighting conditions, you'll see a significant shift in color. If you've ever taken film photos under fluorescent lights, you'd see that everything looked sharply green, when you don't perceive them as being green at that moment. (Digital cameras often make color adjustments, and the sensors are often not as sensitive as film can be.)
Going to an extreme, if you use a red filter on a light source, all colors are going to end up looking brown and grey; switching to red lights does the best at minimizing light pollution and loss of night vision, but at the cost of most color information. That's not bad, just a thing to consider.
Not really, CRI is not dependent on color temperature; 2400K and 2700K incandescent bulbs all have CRI of 100. And, as you said, human brain is incredibly good at adopting to light color temperature. While I would not do color-critical work in candlelight, 2700K and 2400K bulbs are perfect for general late evening lighting and 3000K...3500K is very good for task lights. Higher than 4000K lights should not be a thing in domestic or public outdoor lighting, it's just too harsh and uncozy.
You don't need high lumens, either. As an extreme example, I've done plenty hiking (and patrolling during my military training) in starlight with no artificial light source—the eye is quite remarkable at adopting to darkness. The cities today are overly bright at nights, you could easily halve (or more) the lumen output and be absolutely fine. Even light distribution with no shadowy dark spots is way more useful than overly bright lights. Another personal anecdote, I live on 9th floor and I don't need to turn on any lights when visiting bathroom at night; the light pollution from outside through curtains is enough to navigate around in my apartment.
This could have just as easily been on the dadjokes community.
Oh, I see that now!
I've read that just adding hoods to the lights to keep light pointing downwards would help a lot with light pollution. I'm not sure why we don't do that more
The reason we don't do it more is cost > 0 and the people who make the decisions don't care about light pollution.
The biggest problem I have with LEDs is they're supposed to last forever yet mine die every few months.
It's because the ones you're buying are built with cheap components that are pushed to their limit. If they used oversized components, they'd run cooler and last longer.
Buy Cree branded lights if you can find them. High quality and I've never had an issue.
I mostly second Cree, especially the high CRI versions, which look a lot nicer than the regular versions. The ones I have had lasted a while. However, one went out prematurely not long ago, so they're not immune to poor quality. The generic brands I've bought though look like crap and some barely last two years.
Why did you use a redirection link instead of the original link?
Are you trying to track user interaction?
It's a "gift article" to get past paywall: https://helpcenter.washingtonpost.com/hc/en-us/articles/4403823008539-How-to-use-gift-articles
I've tried the direct link and it is not behind he paywall.
it says the gift article is expired for some reason
Try this: https://wapo.st/3pUUnJu
I'll edit the link for the post. Sorry, didn't realize these type of gift links expire after 14 days.
thanks!
It's just a shortened link, probably copied it for mobile.
But what's the point of shortening it? I want to see the source before clicking on a link.
He likely wasn't responsible for shortening it, Washington post did it automatically when sharing the article. Everything does this nowadays Google maps adds trackers to the url when sharing as well. I agree it's annoying but not many good ways around it.
That makes sense. Thanks!
This is just weird to me, i don't expect to see stars in a city, even before the lights were LED. They're saying the blue light scatters more and that's a problem but if the entire point of the street light is public safety then more light information is a good thing. The cities probably need new studies and information about lumens per square foot though because they're probably working off of old studies with redder light and they could probably lower the intensity and still get the same amount of light information.
Here's another link in case you have issues with the original: https://wapo.st/3pUUnJu
The links are only good for 14 days apparently
view more: next ›