Mixing warm/cold LEDs? - Page 1
Forum section: electronics / beginners

author: kalel
author_rank: Frequent Contributor
timestamp: January 14, 2018, 07:10:35 am
content: Having taken a look at some generic spectrum diagrams for cold LEDs and warm LEDs, would it make any sense to mix cold and warm LED chips to get a somewhat more even spectrum (closer to sunlight)? In a diffused case the fact that they are different colors not matter.I know that there are these "HIGH CRI" LEDs out there, but those will definitely cost more than cheap generic LEDs.

author: Zero999
author_rank: Super Contributor
timestamp: January 14, 2018, 08:52:51 am
content: Quote from: kalel on January 14, 2018, 07:10:35 amWarm and cold LEDs are made by applying differing amounts of phosphor to a blue LED. The CRI will depend on how good the phosphor is. Mixing the two types of LEDs will not give a better CRI.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 14, 2018, 09:00:43 am
content: Quote from: Hero999 on January 14, 2018, 08:52:51 amAlso different types of phosphor, and occasionally additional red LEDs

author: Kjelt
author_rank: Super Contributor
timestamp: January 14, 2018, 09:18:34 am
content: And mixing them will result in a boost of the parts of the "overlapping" spectrum the leds have in common, so still not the desired "flat" spectrum you want.If price is an issue you might want to look at the thin tl5 with electronic drivers and 90 series fosfor, they have almost the same efficacy as leds +\- 90Lm/W and are already pretty diffuse so no extra losses.

author: Psi
author_rank: Super Contributor
timestamp: January 14, 2018, 09:47:09 am
content: From memory its the red parts of the spectrum that is the most lacking in a typical white LED.So if your making a more natural light you might want to source some red LEDs with various red wavelengths to fill in the spectrum.But really, you'll probably end up paying more and having worse results that just forking out $30-100 for some high CRI leds.https://store.yujiintl.com/products/bc-series-high-cri-cob-led-mini-portable-panel-20w-unit-2pcsI'm guessing you were prompted onto this topic after watching BigClive's video.but in case i'm wrong here it is.

author: kalel
author_rank: Frequent Contributor
timestamp: January 14, 2018, 10:03:46 am
content: According to this image:https://newgradoptometry.com/wp-content/uploads/2014/07/visible-light-new-grad-optometry-crizal-prevencia.pngCool white and Warm white does show a significant difference in spectrum, although both are indeed lacking red. But I'm afraid that adding red LEDs might make the output look truly red, rather than "pleasantly mixing". It also shows that Incandescent is very much rich in red comparing to LEDs.

author: Kjelt
author_rank: Super Contributor
timestamp: January 14, 2018, 11:35:47 am
content: Correct but a uniform spectrum has nothing to do with CRI.Look at this brochure for instance, this fluorescent light has also little red and spikes in the spectrum but still has a CRI of 98.https://www.1000bulbs.com/pdf/Philips-TL90SeriesT8-Brochure.pdf

author: kalel
author_rank: Frequent Contributor
timestamp: January 14, 2018, 12:17:05 pm
content: Quote from: Kjelt on January 14, 2018, 11:35:47 amWhat is more important for a "natural" reproduction of colors for the human eye (not camera)? CRI or spectrum? Obviously, humans have a specific sensitivity (e.g. green is most visible). I could be confused about what is important.

author: Kjelt
author_rank: Super Contributor
timestamp: January 14, 2018, 01:43:06 pm
content: CRI.Before LED the CRI was the most important parameter for persons that needed excellent true color reproduction in the shop/office. So cloth fabric designers and shops, printing industry that sort of business all had fluorescent lighting from the 90 series or better.

author: Kjelt
author_rank: Super Contributor
timestamp: January 14, 2018, 05:32:15 pm
content: Quote from: 3roomlab on January 14, 2018, 04:06:56 pmThe colortemperature of the Sun is filtered by the atmosphere, atmospheric conditions(Clouds) and the angle from the sunlight relative to the viewer (sunset, sunrise) and varies from 2000K upto somewhere around 9500K although the temperature of the sun is 5800K pretty weird what filtering can do.

author: phil from seattle
author_rank: Super Contributor
timestamp: January 14, 2018, 05:32:37 pm
content: Yeah but take a look at LEDs with a 5000K or 6000K rating and you'll find a real lack of red. So it's not so simple a just the black body temp.

author: hermit
author_rank: Frequent Contributor
timestamp: January 14, 2018, 05:56:23 pm
content: Take into consideration WHEN you will be using this light also. It might be a good idea to mix them for daylight use and then be able to kill the higher temp light at night.https://www.scientificamerican.com/article/q-a-why-is-blue-light-before-bedtime-bad-for-sleep/

author: Kjelt
author_rank: Super Contributor
timestamp: January 14, 2018, 06:45:14 pm
content: AFAIK 6500K is THE video and broadcast colortemp of monitors/projectors etc.No time to watch the video now but will later, thanks

author: Zero999
author_rank: Super Contributor
timestamp: January 15, 2018, 09:19:07 am
content: Quote from: phil from seattle on January 14, 2018, 05:32:37 pmYes, most white LED lack the deep red end of the spectrum. They often also lack violet, which isn't quite so bad, but it can make thing look less white. I believe the best CRI LEDs, use a violet LEDs, to excite a broadband phosphor and red LEDs, for the long wavelengths.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 15, 2018, 09:22:10 am
content: https://youtu.be/9v48gXbolFU

author: BravoV
author_rank: Super Contributor
timestamp: January 15, 2018, 10:21:31 am
content: I've done similar experiment while ago, like mixing with hot & cold white led , and also some mix bags of colored leds, and ended up with lots of hassles and unsatisfactory results, not to mention the mess as soldering and placing the mix bag various leds with various footprints.At last Dec ended up buying Yuji's 10 watter bulbs, as I'm done with soldering/creating custom pcb and etc, bulb is way more convinient.It was on discounted rate for end of year 2017 holiday season (its over now), and I'm quite surprised as they're really good, to be honest its way-way much beyond my expectation, really.Edit :https://youtu.be/L3LWXznJx_0

author: BravoV
author_rank: Super Contributor
timestamp: January 15, 2018, 10:39:42 am
content: When using real high CRI lighting, there is a nice surprise when you walking around with it inside your house, as some places in our house practically never seen with high CRI lighting.At least to me, it was fun and nice experience as you can see the nice life vivid color of your house that you never seen before. Wifey's jaw dropped out when she saw her cloths closet and at the make up table when the were light up with high CRI light, now she wants it.

author: kalel
author_rank: Frequent Contributor
timestamp: January 15, 2018, 10:41:46 am
content: Quote from: BravoV on January 15, 2018, 10:39:42 amAre different colors easier to distinguish than with "standard" lighting? I assume make up and clothes come in various colors.As for manually mixing things, I agree that is a long shot, I was just curious. Obviously you can't easily mix LEDs (maybe you can if they are tiny) to get specific results, but may or may not be worth experimenting (not if you really need a good result, then buying is best).

author: BravoV
author_rank: Super Contributor
timestamp: January 15, 2018, 11:52:50 am
content: Quote from: kalel on January 15, 2018, 10:41:46 amStill distinguishable though, but its different and one thing is that the differences between colours really stand out, like you can see a sharp & bold difference among colors, don't know how exactly to explain it, but just watch again the video I posted above.As for my wifey, as her clothing are colorful, and one noticeable different is red as lipstick, as she have been seeing for years at her mirror and imprinted in her brain, I guess she saw the huge difference.Quote from: kalel on January 15, 2018, 10:41:46 amMy problem is I worn out experimenting with it as its been years ago, especially different foot prints required different cooling contact points for various leds, the experiment ended up a complete mess and its abandoned.

author: Psi
author_rank: Super Contributor
timestamp: January 17, 2018, 01:30:09 am
content: So i bit my lip and forked out US$98 for 2x 50W 5600k 95 CRI leds from yujiintl (same ones BigClive got)And a PSU to drive them.Lab room lighting needed an upgrade anyway,The current light is a cheap aliexpress 100W cob and cheap psu that is for some reason now driving the LED at 50W (it used to run 100W so dunno maybe its faulty)Hopefully this will make the lab more awesome. From BigClives video i think it will be amazing.Haha, maybe i should keep the current cheap china cob on the heatshink with a switch. So i can show people the difference between them.

author: james_s
author_rank: Super Contributor
timestamp: January 17, 2018, 01:45:43 am
content: You can buy 90+ CRI LED bulbs off the shelf, the Costco near me has Feit high CRI LED bulbs that are only a few dollars each. Several years ago I put a bunch of Cree high CRI recessed can retrofits in my mom's house, I think they were $20-$30 each depending on when I bought them. 10 years ago I was rolling my own LED lighting but these days it's cheaper to just buy off the shelf bulbs unless it's a really custom application.For what it's worth, those Cree retrofits I mention use several rather greenish white LEDs combined with a couple of red LEDs and the result is a very pleasing incandescent-like light. Very few people seem to know anything about CRI but it is what is responsible for the "icky" or "gloomy" look of traditional fluorescent light. Your brain will adapt to nearly any color temperature as "white" but if the CRI is poor things will never look good.

author: kalel
author_rank: Frequent Contributor
timestamp: January 17, 2018, 03:52:00 am
content: Warm white light bulbs are usually much more pleasant for the eye than the cold-white (this could be individual), even though the warm ones appear more "yellow" (as they are supposed to) than actually white. But as for the reproduction of colors, it might be slightly better when there is a warm white bulb + cold white bulb, although I do not have much to compare the combination with. I do not have any of those high CRI units of any type, and if I do run into one at an affordable price, I will definitely consider it (the discussed price of the yuji is too high just for my personal curiosity - which is not professional use of any kind).In the end, I assume most of it is personal preference unless used for some type of commercial (or hobby) work where we want to see colors as accurately as possible. As a random example, a painter might want to see them as accurately as possible?But if it's a commercial product you buy, the way you will see it at home will still depend on your own light.Of course, the actual topic was whether or not mixing different LEDs could get you a positive effect on seeing colors (existing, cheap LEDs), but all of this is related.

author: kalel
author_rank: Frequent Contributor
timestamp: January 17, 2018, 03:57:17 am
content: Quote from: BravoV on January 15, 2018, 10:21:31 amRegarding this video athttps://youtu.be/L3LWXznJx_0?t=167Is the generic LED really supposed to look that washed out? Is it because of the camera being set to sunny - would it look better on a different setting? Or is it just because the image on the right looks much better, so the one on the left seems worse than it would actually look by itself?

author: BravoV
author_rank: Super Contributor
timestamp: January 17, 2018, 05:25:58 am
content: Quote from: kalel on January 17, 2018, 03:57:17 amAgain, this is purely subjective, also I'm not an expert in this matter, just share what I've experienced, think and "feel" regarding this topic.The screen comparisons you pointed out above actually doesn't reflect what I've experienced, at least to my eyes.Here the original, to be honest, the left side is actually very pale, abit darker and also less saturated. May be they deliberately made it worst and to make the right one stands out, not sure though.Now, using above image, I modified the left side with more saturation and light up abit on the brightness that I think and "feel" its more realistic and fair comparison between ordinary led and high CRI light source. Remember, this is purely subjective, just trying to show what I've experienced thru my eyes.Now, regarding lighting up with Yuji leds, the obvious one is the skin tone, no argument about that. But what I want to point out is other details. Pointed out with arrows, 1st look at his tshirt, the left side is like greenish brown like military camo tshirt, while the right one is clearly brown, my brown coloured stuff also look real brown. Also the white wall at the background, my wall is white, thats what I see when using Yuji bulb I bought. Also the most part that I like is the wooden stuff, watch closely the wooden frame hanging at the wall, my house has wooden furniture, they really light out and looks really nice.As above mentioned by other poster, actually our eyes will gradually adapt and sort of accept white even they're not perfect. Here another example from that video, I did increase the brightness and add abit of saturation to make it fair comparison with below example. Just look at this photo for a while, don't scroll down yet, stop at this photo only for few minutes, my eyes are gradually accept its good enough white. Until ........ when I saw the scene like this one. The difference is too much to ignore. Let alone the skin tone, just look at the wooden furniture and the white wall compared to above photo.The key to see and feel the "huge" difference is to have two sources in hand so you can compare, like Psi's plan, to have old led as comparison to see the difference once the new one is installed.All I can say is you need to see it "AND COMPARE" to appreciate it, especially at the places/corners in your house that you already used to see them for years using low CRI light source all this time.Hope this helps.

author: Moshly
author_rank: Regular Contributor
timestamp: January 17, 2018, 08:17:27 am
content: You can get dual white strips and dual white COB LEDs.I find 2x cool white +1 warm white strip work well as under shelf lighting for my workbench.Doesn't look too blue / too yellow (to me).You also have natural white 4200k.Also, the same guy has made this ->I'm thinking of doing a similar thing with cob strips in a transparent top case.

author: BravoV
author_rank: Super Contributor
timestamp: January 19, 2018, 04:17:22 pm
content: Quote from: 3roomlab on January 19, 2018, 12:51:15 pmThere you go.Yeah, the VTC one has the best CRI at 98, too bad currently there is no light bulb model that uses that VTC type, only the BC type, but its still really good imo.