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Author Topic: What do I need to be able to display light spectrums?  (Read 12272 times)

Ernst Dinkla

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Re: What do I need to be able to display light spectrums?
« Reply #20 on: February 04, 2014, 10:53:45 am »

http://www.olino.org/advice/us/overview

Repeat the jobs they have done so thoroughly?

BTW: probably expensive but a LED with 93 CRI by Philips for medical tasks:
http://www.burtonmedical.com/products/examination-lights/nova-exam-led/


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http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
January 2014, 600+ inkjet media white spectral plots.


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WayneLarmon

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Re: What do I need to be able to display light spectrums?
« Reply #21 on: February 04, 2014, 01:16:03 pm »

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http://www.olino.org/advice/us/overview

Repeat the jobs they have done so thoroughly?

It looks like they have only tested consumer bulbs and not on LEDs that are designed for photographers, which remain an unknown wilderness.  (Until somebody buys one and tests and reports on it.)   And I don't see many (any?) bulbs that are for sale in stores in the US.

But thanks for the link.  I did not know about this site.    There is lots of information there.  It is nice that they also include regular tungsten bulbs for reference.
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digitaldog

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Re: What do I need to be able to display light spectrums?
« Reply #22 on: February 04, 2014, 01:59:42 pm »

It looks like they have only tested consumer bulbs and not on LEDs that are designed for photographers
Where do they specify the output? Are they just super bright but using similar technology to tested consumer blubs?
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MiSwan

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Re: What do I need to be able to display light spectrums?
« Reply #23 on: February 06, 2014, 08:48:43 am »

The typical 80 CRI (useful value or not) seem to be a glued fact to almost any LED I've measured.

The spectral curve that Andrew shares is exacly the same I get for both cheapos as well as "better brand" LED's. At the moment I'm on my way to check a Ferei divinglamp (to be combined with a GoPro cam) which holds 3 LEDS (the extremely powerful Cree XLamp XM-L2 LED). The diving lamp has three settings and the most powerful setting deliver about 2900 lumen! Un piccolo bastardo di luce! Madonna! You can get a nice suntan even underwater.

Italian or Finish site, make you choice ;)
http://www.fratellicordi.it/1/w163_7401102.html
http://www.valostore.fi/tuote/sukelluslamppu_ferei_w163/

(Some people build divinglamps based on Soluxbulbes, but 50 W on a 12 V battery…not surprised that the LED is a real gift nowdays)

Ferei's own spectral information for the LED mentioned, show almost exacly the same spectralcurve that Andrew posted.

http://www.cree.com/led-components-and-modules/products/xlamp/discrete-directional/xlamp-xml2

It has been a lot of talk about that little LED, which can be bought for 8 USD each for making your own stuff if you know how to deal with it:
http://www.ledgroupbuy.com/cree-xm-l2-white/
http://www.ledgroupbuy.com/exotic-leds/

Some people use this LED and combine it with other singlecolors LED's to maximize spectral enviroment for reef /aquariums. These guys measure spectras like maniacs to tune light in for corals and all the rest for an optimium environment. You see, geeky crazy people everywhere. Who cares about a shitty aquarium? I don't get it. But I don't mind the info though!

http://reefbuilders.com/2012/12/11/xml2-crees-highest-performing-led/
http://playsofrays.blogspot.in/2012/12/leds-made-easy.html
http://reefbuilders.com/2014/01/30/giesemann-futura-s/

I doubt that spectral distribution would be different with any of the Photo panels. The choice of CCT seem to be the only option. Anyone measured any of the photopanels in regards of spectra? Another question – or more of a wish – …. if it's possible to convert a Solux to a LED….. shoulden't be impossible, no?


Off topic: does anyone know what part of the spectral distribution that gets lost under water and which is enhanced? I'm talking Maldive's water now. Perhaps a dip in the cyan part of the spectracurve (of a LED lamp) would be a good thing in that water nightdiving? I'm not sure how far from the lightsource the "filtering" from the water sets in on the spectral distribution of any light. Would be nice to know. Anyone at the Maldives here at this board? (Ah… so you've got better things to do there – I don't blame you)

Mi
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BCRider

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Re: What do I need to be able to display light spectrums?
« Reply #24 on: February 06, 2014, 12:21:18 pm »

...Anyone measured any of the photopanels in regards of spectra?...

Well, I think that is the question of the thread...

Spectra of conventional LED's are well known and show the characteristic we published earlier.

Personally, I doubt the "photography LED panels" are much better.  I say that because none seem to specify the output spectra.  I can measure the spectra and would be happy to do that if someone local (Vancouver, BC) had one to measure...but I don't expect to buy one and measure it any time soon (given my low expectations and their high prices).

The TW Cree bulb mentioned earlier should be an improvement.  But based on the patent application they are very focused on raising the CRI number only (not producing a good spectra!).     The patent is focused on a single very narrow width notch filter (10-20nm only) optimally placed at a wavelength to generate maximum boost in the CRI number.   Of course they have weasel words to generalize the patent but it is clear that isn't their focus.   So the TW bulb isn't likely good in absolute terms although probably better in relative terms.   That's just IMO, if I can get one to measure I'll do it.  It isn't available so far in the local HD stores.




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digitaldog

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Re: What do I need to be able to display light spectrums?
« Reply #25 on: February 06, 2014, 12:31:54 pm »

It's a shame that CRI is used as it is, mostly for marketing to the unsuspecting buyer. It's much like lumen for selling projectors, megapixels for selling cameras, huge contrast ratio's for selling displays or the billon's of colors it is said to produce. All marketing, much not useful.
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Ernst Dinkla

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Re: What do I need to be able to display light spectrums?
« Reply #26 on: February 07, 2014, 08:01:34 am »

It's a shame that CRI is used as it is, mostly for marketing to the unsuspecting buyer. It's much like lumen for selling projectors, megapixels for selling cameras, huge contrast ratio's for selling displays or the billon's of colors it is said to produce. All marketing, much not useful.

The olino.org site gives at least a good explanation of the CRI flaws and adds enough other information to judge the spectral distribution of a high CRI lamp.

The development that might give us full spectrum LEDs is the one done by Rosenthal at Vanderbilt Uni.
http://news.vanderbilt.edu/2012/05/quantum-dots/

Philips meanwhile makes hybrid LED Fluorescent tubes that could become high CRI lamps in time. Expertise enough there.

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http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
January 2014, 600+ inkjet media white spectral plots.
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BCRider

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Re: What do I need to be able to display light spectrums?
« Reply #27 on: February 07, 2014, 01:35:11 pm »

Quote
The olino.org site gives at least a good explanation of the CRI flaws and adds enough other information to judge the spectral distribution of a high CRI lamp.

They reference a CIE Technical Committee studying this question:  "The result of the three investigations show that there is a low to no correlation at all between the computed CRI and the visually determined differences in color. The TC (CIE Technical Committee) comes to the following remark:  the CIE CRI is in general not applicable for a ranking on color rendition when white led sources are part of the observed illuminants."

The CIE Technical Committee apparently recommended developing a new color rendering index standard.  
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WayneLarmon

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Re: What do I need to be able to display light spectrums?
« Reply #28 on: February 07, 2014, 09:26:02 pm »

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...the CIE CRI is in general not applicable for a ranking on color rendition when white led sources are part of the observed illuminants.

Ya think?  In case the quoted statement is a bit opaque, here are two graphs from the referenced page:


Spectrum of light with a color temperature of 3084 K and CRI = 94


Spectrum of light with a color temperature of 3076 K and CRI = 83

http://www.olino.org/us/articles/2009/11/30/a-close-look-at-the-color-rendering-index-cri-or-ra


Meet the new boss,
Same as the old boss.
Won't get....

Ah, you know.

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Ernst Dinkla

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Re: What do I need to be able to display light spectrums?
« Reply #29 on: February 08, 2014, 11:34:36 am »

The test panel results quoted in the link had a link to the PDF of the test conditions The test was done with equal 200 Lux illumination on the objects for every Kelvin grade choice of lamps. The PDF did not refer to the Kruithof curve of preferred Kelvin grades for different light levels and there was no compensation for that phenomenon in the test . The low rating of the tungsten and halogen lamps shown there is more a (negative) confirmation of Kruithof's discovery  80 years ago than bringing CRI to its knees. Not that the CRI index is good but this test was worse.
http://www.olino.org/us/articles/2009/11/30/a-close-look-at-the-color-rendering-index-cri-or-ra

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Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
January 2014, 600+ inkjet media white spectral plots.
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smilem

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Re: What do I need to be able to display light spectrums?
« Reply #30 on: February 20, 2014, 04:36:00 pm »

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Um, do you know of anybody that is measuring LED lamps?  The only reason I want this is because nobody else is showing spectral plots and CRI ratings of LEDs.  We all pretty much know what CFLs are good for by now but LEDs are a wild card.  (i.e., some of them now have smooth spectrums, just like tungsten.  But maybe not shaped quite right.  Which may be fixable with a Rosco gel.  Maybe.)

Thanks.

I don't think anyone is interested and CRI isn't the most reliable way to measure light quality. The usual consumer doesn't care about light quality. The best LEDS are from Sharp (Japan), they are called Mega Zenigata. Have fun.
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