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Spectral Power Distribution for Sources

LED SPD

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#1 Will J. Løkken

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Posted 30 October 2016 - 10:24 AM

Lately I've heard more and more people talk about the qualities of new LED lights, that are supposedly as color correct as a kino-flo.

I guess the SPD we are going for is to be a close as possible to daylight or tungstens;
A somewhat even distribution of all colors;

 

Screen Shot 2016-10-30 at 16.12.38.png
Screen Shot 2016-10-30 at 16.12.41.png

But how close to this do the newer LEDs come -- and are there any particular brands of LEDs that are better than others?
It's hard to find much information online about the SPD, only the CRI is available, and not even for all.

I came across this in the ASC magazine. CRI 95+, but the SPD looks like something I wouldn't want to use as a key light. 
Screen Shot 2016-10-30 at 16.18.46.png

Do any of you know what the SPDs of a kino-flo and a HMI is?

Thanks,


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#2 Phil Rhodes

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Posted 30 October 2016 - 12:18 PM

I don't have a measurement of a real Kino-Flo, but I have some other stuff. Notice that most (all) of them are very far from ideal.

 

Osram HMI 575W Sel UVS:

 

HMI-UNFLT_01_6423K_SpectralDistribution.png

 

Aputure COB-120T:

 

APUTURECOB120_01_2927K_SpectralDistribution.png

 

Overcast daylight:

 

DL-OVCST_01_6026K_SpectralDistribution.png

 

Tungsten halogen:

 

TUNGSTEN_01_2809K_SpectralDistribution.png


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#3 Yann Cainjo

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Posted 30 October 2016 - 03:28 PM

An independent study on photometric and colorimetric performance of LED lights published by CST in France (English & Spanish translations included) with reference data from kino, tungsten and hmi jokerbug :

http://www.cst.fr/wp...Internet-v2.pdf

It is an update of a former study (2014, only in French but same layout) :

http://www.cst.fr/wp...aj-20-01-15.pdf

Yann Cainjo
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#4 Will J. Løkken

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Posted 31 October 2016 - 12:21 PM

Phil & Yann,
Thanks both of you -- this is very helpful!

I'm surprised about the SPD for the Joker HMI. I wonder if it's the same for ARRIs HMIs. 
- Looks much like the Osram HMI above in your post Phil


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#5 Phil Rhodes

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Posted 31 October 2016 - 02:36 PM

I would anticipate most HMIs to look the same; they're either the same bulbs, or bulbs using fundamentally similar construction. They drift somewhat as they age.


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