kelvin question

[nitebrite]

i have had a 6500k 98 cri bulb that emits uva/uvb for my desk lamp for a long time. it was always hard on my eyes but made everything look as it was. so i got a high end led lamp. it is 3000k,probably low cri i am guessing. it is not hard on my eyes but everything looks very yellow. well, obviously it is 3000k. my question is will i get used to the difference? since i really like this lamp. most people are used to incandescent lights but i am wondering how hard it is to go back to that kelvin once one is used to daylight spectrum.

also, will it help if i set my display lower than 6500k(srgb)?

edit: adjusting my display to 5000k and lowering the contrast made the display usable. now i assume the display is way off proper colors? i am just wondering if this lamp is usable.

thanks.

 

[THE_dAY]

I like the warmer light for indoor/home lighting, it adds comfort in some sort of way. I feel it's easy to get used to.

I've recently added some calibration profiles to my laptop's display ranging from 6500K down to 4500K in ~250K increments.
I now exclusively use the calibrations from ~5250K to 4500K.

I haven't used my laptop outside in the daytime but if I did I'd probably go up to a higher Kelvin profile but for indoors its perfect at the lower Kelvin levels.

I've tested colors (images/videos) using the multiple profiles and don't feel that the colors are off at the lower Kelvin's they're just slightly warmer like viewing an object in late afternoon sunlight.

 

[blasterman]

UV-B?

 

[Anders Hoveland]

i have had a 6500k 98 cri bulb that emits uva/uvb for my desk lamp for a long time. it was always hard on my eyes but made everything look as it was. so i got a high end led lamp. it is 3000k,probably low cri i am guessing. it is not hard on my eyes but everything looks very yellow. well, obviously it is 3000k. my question is will i get used to the difference? since i really like this lamp. most people are used to incandescent lights but i am wondering how hard it is to go back to that kelvin once one is used to daylight spectrum.

This just goes to show that the CRI index does not have much to do with how "harsh" or "soft" the light is on your eyes.

Some of it could potentially be caused by glare. Have you considered putting a light diffusor over the lamp?

Two other possibilities you may consider are that you may be finding the 6500k lamp to have too much blue/green, which may be less comfortable for your eyes.
Another not unlikely possibility is that the UV radiation is causing your eyes discomfort.

My suggestion to you would be to try using a frosted halogen bulb (the ones that look just like a regular light bulb) along with either the LED light your already have, or a bluer "5000K" LED bulb. Halogen has excellent color rendering, a little better than normal incandescent. You might also consider a halogen with a Revel filter ("natural daylight"). The yellow phosphor in the LED gives off light in a similar region of the spectrum to where the Reveal bulb filters it out, so there should not be much loss of CRI, assuming the intensity ratio of Reveal to LED light is optimal. I actually use this combination in my bathroom and am satisfied with the resulting white light.

Unfortunately, with the current white LED bulbs available, there is no way to achieve higher CCT without sacrificing CRI.

I have also heard good reviews about the Nikken KenkoLight Full Spectrum LED Desk Lamp, but have personally never tried it.
http://ecowellness.wordpress.com/20...-sun-light-a-discount-for-newsletter-readers/
But I would be cautious before buying it, because there does not seem to be any actual spectrum graphs available, and it is expensive.
Typical white LED's that are being marketed as "full spectrum" usually look something like this:
http://www.advancedaquarist.com/2012/7/lighting_album/image025.png
http://www.epistar.com.tw/smarteditupfiles/ch_trad/technology/technology_02_08_7.jpg
(not exactly like sunlight, is it?)

 

[blasterman]

not exactly like sunlight, is it?)

Neither is any fluorescent tube, although if you're a head of lettuce you might not notice the difference.

At ~85 CRI the latest neutral LEDs I've used look much better than any high CRI fluorescent tube. I'm otherwise confused at what the OPs question is because CCT (color temp) has nothing to do with LEDs. Lamps based on the high CRI, ~4500k Citizen emitter have been discussed here before. That would have been a better choice.

However, if we're attributing UV-B as part of the visible color spectrum of CFLs perhaps we should move this to a theoretical physics forum because it might be awhile before Cree invents a tachyon emitting phosphor 😱

 

[Anders Hoveland]

I have already posted this before, but if you are willing to shell out thousands of dollars, you can buy yourself a MoleLight LED. They have the fullest spectrum I have seen from any commercially available white LED product:
https://f1ccdd38-a-62cb3a1a-s-sites...ymNn5SxX2h8dssb5w7ID3vhGEckLb5&attredirects=0

Cree also came out with a 97 CRI LED chip:
http://incoherentphotography.com/uploads/Screenshot-2011-10-18_23.38.48.png
http://www.bridgelux.com/products/decorarray.html
(although the efficiency is much worse than regular white LED chips)

 

[nitebrite]

the sunlight cfl put out 550 nanometers of uva and uvb. it was actually a bulb meant for reptiles. indeed the glare was the issue. even though it was completely enclosed in a white reflector. this lamp seems better to me. cfl seems very harsh. especially at high cct.

i have halogen like you described in my bathroom as well. quite frankly it is the best light in my house! everywhere else i have cheapo cfl's. they are not very pleasant but they do save energy.
i would certainly go get a halogen lamp. my problem with them is i always broke the socket at some point and the bulb needs to be changed often. they are better light i will agree. of course that is for a different thread.

i traded the lamp for the 4500k version and i do like it better even if it is just in my mind. it has 2 cree xp-g and it says 95 cri. the cree comes in different cct and cri? i think these specs are bs. it has dimmer which is welcome since it is very bright on full. nonetheless it seems better than the cfl it replaced.

 

[nitebrite]

i just put back the cfl with a diffuser this time. i would say it represents everything much more accurately than the xp-g. i do not think the xp-g is 4500k or 95 cri. i do think this lamp was overpriced. it is ok but not so special.

 

[blasterman]

I've spent a lot of time working with high CRI fluorescent tubes and CFLs in color correction and know what they look like. Not sure what type of lamp you have here, but if it claims to be '98 CRI' and 'daylight' I'd be willing to guess it's just a rebranded high CRI CFL sold in a pet store at a price markup. They do the same for plant lights. There's no magical spectrum emission and the spectrum is likely no different than the high CRI tube in the graphics arts area at work. Same phosphors - different marketing - price mark-up.

While these bulbs do have a high CRI and produce strong color rendition the downside is they tend to exagerate colors because of the dominant spikes. In a way it's addictive in terms of color rendition given how we are accustomed to bland lighting indoors, and is why these lights are often claimed to stimulate work environments and productivity. Incan and halogen light sources have higher color rendition but it's locked up in a flood of yellow light. After years of working in color correction I'm no longer fooled by spikey light sources with high CRI although I admit it does wake you up, and after working under this type of light source it doesn't feel right moving back to a lower quality artificial one. The problem with LEDs is that the only reliably decent color rendition in retrofits will be warm-white. There are neutral white LED bulbs that do have high CRI, but they are typically special order. 95 CRI in a single XP-G package at 4500k.......not so sure about that.

 

[nitebrite]

blasterman, is the led in fact better if i give it time to get used to it? i mean i used incan for decades. like you said after the color match bulb it is hard to go back to. it really wakes me up just like ottlite,verilux say! i fixed the issue that brought me here with a diffuser. thank you for that suggestion anders. the led is yellow,has a hotspot and casts shadows. that just does not look great to me. is a different led lamp in order perhaps? i can't justify keeping this given what it cost if i cannot get used to it.

 

[SemiMan]

For a desk/reading like, a warm white light is not a good thing. If you do not have adequate blue, then your pupil does not close properly and you are left with poor depth of focus. This will cause eye strain as you move your eyes over things at different distances (and your computer perhaps). On a desk, you can quickly move your eyes between things with a 3:1 to 4:1 ratio in distance. The more depth of focus you have, the better. That takes a cool light.

I am curious as to what other lights you have around and on when you are using the high cri cool white CFL. If your other room lights are warm, then you may have an artificially wide open pupil and yes, the CFL may seem overly bright. The issue will be a bright spot of cool white light in a cloud of warm light ... or perhaps no other lights? If this is the case, then diffusing out the light as suggested will help.

Unlike what Anders stated, you don't need to spend thousands on a wide spectrum LED light that he just discovered. Just find someone who is using a Xicato Artist series module at 4,000K or who will sell a version of their light with one. That said, for a desk lamp, you don't need perfect CRI unless you are looking at art/color samples. You can guy 85+ CRI nichia 4500K leds which will be fantastic, but just mixing neutral and cool white can result in a very pleasant light. Again, you still need to be careful about what the dominant light stimulus is in your room or you may still find the desk lamp harsh.

 

[nitebrite]

it is the only light on when i am using it. i did go ahead and use a diffuser and the glare is gone. when i am talking about led lamps i mean complete desk lamps with a non replaceable led module. the 4500k one was not nearly as white as the 6500k cfl. i also want a diffused soft light and these lamps have optics. a better idea may be to get a standard base led bulb and use it in a corresponding fixture. then i can easily choose the cct and diffuse it. i am not sure i see these led desk lamps as being so great at this point. for one thing i strongly feel any bulb could fail and should be replaceable. however i am not convinced led light is superior for my purposes. it is a lot easier to find out with screw in bulbs though. unless those are in fact somehow inferior to the complete desk lamps featuring led's. i have not kept up on this stuff other than flashlights.

 

[UnknownVT]

If it helps - our eyes adapt to the ambient light levels according (empirically) to the Kruithopf Curve

I have always found for looking/examining colors the color temperature seems to be more important than the CRI (Color rendering index) within reason. Even though our eyes are supposed to "like"/think about 2700K incandescent lighting in normal household conditions - I still find it hard to distinguish between navy and black or see yellow print on white.

However using either 6500K or 5000K CFL - even though I know they are only about 82CRI - makes viewing photos, examining colors etc. much better for me.

Personally I prefer 5000K (which is supposed to be closer to "sunlight") over 6500K which I find slightly "blue".

However one should be aware of:

The CIE positions D65 as the standard daylight illuminant:

[D65] is intended to represent average daylight and has a correlated colour temperature of approximately 6500 K. CIE standard illuminant D65 should be used in all colorimetric calculations requiring representative daylight, unless there are specific reasons for using a different illuminant. Variations in the relative spectral power distribution of daylight are known to occur, particularly in the ultraviolet spectral region, as a function of season, time of day, and geographic location.
—ISO 10526:1999/CIE S005/E-1998, CIE Standard Illuminants for Colorimetry​

​

So I use 6500K CFL for lighting to take photos under.
5000K CFL for viewing/examination.

Regular household lighting is 2700K CFL, including the room with my computer monitor - but I do have a shade.

 

[jtr1962]

Honestly, there's no point trying to get "used to" your new 3000K LED. As others have said, your ocular system doesn't function optimally under that type of lighting. LEDs can easily imitate any CCT fairly well, so little point in being wedded to incandescent-type lighting, or trying to adjust to it. Truth is once you get used to more natural lighting, it's impossible to go back to yellowish lighting, nor is there any good reason to.

 

[nitebrite]

thank you guys. i am exchanging it for a lamp with a standard base socket. this led lamp was $750! there is a very nice lamp with a standard socket for much less that suits me fine. i cannot stand that directional yellow light with the bright hotspot. that's it. i have to say this particular cfl is far superior lighting than this particular led. perhaps other led's are better but i do not have the ability to try them all. i did fail to mention i am using this on my desk for professional photo editing. so i was obviously barking up the wrong tree. with the diffuser the cfl is great. especially compared to this led lamp. i am happy i tried the latest technology though.

 

[UnknownVT]

thank you guys. i am exchanging it for a lamp with a standard base socket. this led lamp was $750! there is a very nice lamp with a standard socket for much less that suits me fine. i cannot stand that directional yellow light with the bright hotspot. that's it. i have to say this particular cfl is far superior lighting than this particular led. perhaps other led's are better but i do not have the ability to try them all. i did fail to mention i am using this on my desk for professional photo editing. so i was obviously barking up the wrong tree. with the diffuser the cfl is great. especially compared to this led lamp. i am happy i tried the latest technology though.

$750?! holy-m....

To look at/examine photos, I use a desk-lamp that is about $5-8 from WalMart and a 5000K CFL either GE or UtiliTech (Lowes) ~82CRI and these CFLs are about $2-5/each.... 😱:huh:

To photograph indoors I use 2x 100w equiv (26w) 6500k GE CFLs (82CRI) - that I got on close-out for <$2 each..... (in desk lamp holders as above)

I think I am quite critical about my photos, since I take a lot -
but I am no authority - so am quite happy to be corrected.

 

[Anders Hoveland]

Incandescent and halogen light sources have higher color rendition but it's locked up in a flood of yellow light.

It probably would not be worth the trouble, but theoretically to get the best quality of light, wouldn't it make the most sense to combine halogen with a "high CRI" fluorescent that just has the green and blue phosphors? The halogen would do an excellent job taking care of the red-orange-yellow part of the spectrum, and the green-blue phosphors from the fluorescent would raise the CCT.

Consumers should probably know that nearly all of the "high CRI" fluorescent bulbs still have very spikey spectral graphs. The CRI index has recieved much criticism because it is not always an accurate measure of how well a light source will accurately render colors.
Here is a typical fluorescent bulb that is marketed as high CRI, the spectrum is still obviously not anything like natural sunlight:

There do exist some fluorescent bulbs that actually are full spectrum, just look at this: http://www.truesun.com/proddetail.php?prod=TrueLite_full_spectrum_light
I will still not be buying these because, while they may be very similar to sunlight in the vissible spectrum, fluorescent tubes still give off UV, apparently at higher levels than sunlight for certain frequencies (particularly at 253.7nm, some 365.4 (UVA), and a tiny ammount of 184.5 that manages to get through the glass tube). I am not sure what exact frequency is causing me problems, all I know is that my skin seems to be more sensitive to fluorescent bulbs than sunlight. I think this type of problem may be much more widespread than commonly realised, but most of these people have such a low sensitivity they never really notice it, or never make the association between fluorescent lighting and their slight skin irritation. And even if fluorescent lighting is no worse than direct sunlight, it still is probably not a good idea to be exposed to UV all day, especially for people who work long hours under artificial lighting.

 

[nitebrite]

it is a real sunlight bulb. not what is sold at lowes. with a nice dose of uva/uvb. perhaps i will be sorry. however lab technicians have worked under chroma 65 tubes for thousands of hours. d65 98+ cri is what is used in a color match lab. i will say i am addicted to it now. the xp-g looked horrible to me. so does incan and so called daylight 82 cri cfl's. with the diffuser now it is simply superior light to me. led's like this exist but they are thousands of dollars afaik. btw, ott lite claims to be 5850k at 90 cri. that does not qualify it as a color match bulb and i can see the difference. this is why all the lab folks end up retrofitting their homes with chroma 65 tubes. it is like a drug. once someone is used to it nothing else looks right. of course i wouldn't say sunshine is "wrong". i do however wish i could have liked the led. that was such a cool fixture. i knew there was no way i would get used to it and you guys confirmed that.

 

[Anders Hoveland]

While you might think that a 2700K incandescent light causes color distortions, it does so in a consistent way, which your eye can compensate for. Why do "whites" look about the same at different times of day, even though the actual colors vary quite a lot? The "von Kries hypothesis"explains this, suggesting that the three receptors in the eye can change their "gain" in different environments in order to compensate for different lighting conditions. CFL's and other sources distort colors in a way that your eye doesn't easily fix, for instance by creating "spikes" of extra green that distort particular colors.

Apart from natural sunlight, the best light source available for painting or viewing art today are from SoLux, which is just a halogen incandescent with a unique coating formulation. These bulbs have a 98 CRI at 5000K CCT.
http://solux.net/cgi-bin/tlistore/infopages/index.html

This spectral graph shows how closely SoLux filter bulbs match natural daylight:
http://www.photoanswers.co.uk/upload/6867/images/Solux versus Daylight at 3500K.png
very impressive

 

[AnAppleSnail]

My main experience with color perception and CCT is that mixing CCT feels strange - that is, if you have one area at 6500K CCT (Your working computer) and another area at 3000K CCT (Your working area) then you'll feel funny looking between them.

I've been a hobby photographer for a few years, and while I haven't made a cent, I've learned a lot about color perception and lighting. In the kitchen I run 'warm white' CFLs (Around 3000K CCT) and some neutral-white LEDs (Around 4200K CCT) and recently added a block of XM-Ls (6000K CCT) as an experiment. It worked great, despite my above note. Why?

Because they mixed above me and led to better color perception (And brightness, of course). The CFLs are in awful fixtures, but each LED color ceiling-bounces to distribute the light. Certainly not as efficient as it could be, but adequate. I believe that Cree takes advantage of this CCT-mixing to give higher CRI (And presumably greater color perception) in their EasyWhite series.

I have learned:

1 Brighter is often better. The closer you are to daylight, the nicer I fell.
2 Each person has preferences. They may even change; this winter I have started to gravitate towards higher CCT tints. Thankfully, technologies are coming out to make this possible with decent color perception.
3 I have gotten good results from blended CCT, but I still feel funny if I can see splotches of varying CCT.
4 Light management is critical. Visible glare and poorly chosen fixtures cause a lot of problems (From headaches to house fires).

As an unrelated note, I have learned this about photo editing:
1. I assume that you're editing on a computer. All computer screens look different, and even CMYK printing varies more than I thought it would.
2. If you are comparing in-hand samples (Hence the high-dollar lighting) to your screen, see (1). You can calibrate your screen to some extents, even my Dell screen came with color space information that I didn't bother to read. If you've already done this, then we're on to making it work anyway.

If color is super-critical to your tasks, a halogen bulb is a decent fit. Just be sure not to set things on fire! And have spare bulbs around. The super-color-rendering bulbs start to get surprisingly pricey. I don't know if LED can give truly excellent color rendering, but I have had good luck with high-CCT high-CRI LEDs that are starting to become available. The recently-hailed Nichia 219-something is one example.

PS: There are UV-filtering glass things that might delay the onset of cataracts by a few years. Don't excessive UV-A and UV-B lead to those?

I'd like a bit more information about what tasks you're doing before I suggest you blow a few hundred on another light. It seems that what you have works well - is this so?