Fun with a Sekonic C-7000 Spectrometer For Kelvin, CRI & Other Measurements of LED's

BVH

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Fun with a Sekonic C-7000 Spectrometer For Kelvin, CRI & Other Measurements of LED's

Picked up a new toy.............. or rather an indispensable measuring tool today. I've been what I call a connoisseur of light for a decade or so now. My sweet spot is 5500K. I've just not been able to get into the neutral or warm Whites. There is only 1 incan bulb in my house. Everything else is LED 5000K or 5500K. Now I can precisely measure all of my home, car, searchlight and other lights' color temps and the REAL CRI, not just the averaged number usually quoted for marketing purposes. I've learned quite a bit over the last week while researching my purchase. The typical CRI number we see is the calculated average of 8 colors chosen decades ago by a Body in France, the name escapes me now. It represents how close a light source comes to the spectrum emitted by Tungsten incandescent light. CRI of Tungsten light is 100 on the CRI Scale. Extended CRI adds another 7 colors to the mix and the Sekonic 7000 meter has the capability to measure and display the additional 7 additional colors. The more color samples that are taken, the more accurate your CRI is going to be. But even CRI is a bit outdated and there have been and are processes in-motion to use another standard or two. There's a lot more to it but i won't get that deep. Suffice to say that below, the first 2 pics are of readings of the Sun. The first shows the Color temp in Kelvin (Tcp on the meter) of the Sun at 3:15 PM. Don't pay attention to any of the lux reading as I did not set up for a precise Lux measurement. The next pic shows the CRI RA average of the Sun calculated on only the first 8 colors in the bar graph but it also shows specific individual CRI readings from all 15 samples. The higher the bar graph and number to the left, the higher the CRI of each of the sample colors and the closer to the Tungsten standard the measured light source is.

The 3rd and 4th pics are of the same type of measurements of the Group Buy GT I recently received on HIGH, not Turbo. The 5th and 6th pics are of the GT on Turbo. Notice how the R9 Red is absent from the GT and is actually a minus number.



Sol at 3:15 PM Dec 12 Text Mode Kelvin Temp (Tcp)




Sol at 3:15 PM Dec 12 Bar Graph Mode CRI RA




GT at Top of Ramp Text Mode Kelvin Temp (Tcp)




GT at Top of Ramp Bar Graph CRI RA




GT at Turbo Text Mode Kelvin Temp (Tcp)




GT at Turbo Bar Graph Mode CRI RA

 
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NoNotAgain

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Re: Fun with a Sekonic C-7000 Spectrometer

Congratulations on the meter. I had access to the C700U Sekonic. It did more than I needed as does your C7000.

I preferred the Gossen Mavospec base due being able to get spot readings. Both are great tools, but it comes down to personal preference.
 

Modernflame

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Re: Fun with a Sekonic C-7000 Spectrometer

This thread is full of potential. Thank you for the informative readings! I'm hoping to see the measurements taken from other flashlights.
 

BVH

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Re: Fun with a Sekonic C-7000 Spectrometer

I'm under the impression that typical XBO/Xenon Short Arc lamps have CRI's in the 90's. It will be fun to confirm this on my searchlights.

I would be more than happy to measure lots of light sources for people if they send them to me. Send complete lights, bare LED's, commercial bulbs, whatever you might want measured. I have programmable current limiting power supplies so I can power up bare sources so to speak. Example: LED's on stars as long as I can get a reasonable sized contact area or u attach wires to it. I can provide Kelvin and CRI/extended CRI measurements and, although I do not quite understand them yet, info on where the source is in relation to:

CIE1976
CIE1931(CIE1964)
XYZ
xyz
u'v'
λp (Peak wavelength)
λd (Dominant wavelength)
Pe (Purity)
PPFD

Maybe a database/repository of sources and their measurements could be kept on the site.
 

BVH

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Re: Fun with a Sekonic C-7000 Spectrometer

Yesterday, the Sun at 3:45P was 5001K and 99.5 CRI. Today at 10:45 it's 5401K and 99.4 CRI.
 

maukka

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Re: Fun with a Sekonic C-7000 Spectrometer

Good to see the GT has a nice rosy tint. Thanks for the measurement!
 

BVH

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Re: Fun with a Sekonic C-7000 Spectrometer

Todays 10:45 Sun was 5409K and 99.4 CRI
Todays 12-noon Sun was 4901K and 94.1 CRI
Todays 2 PM Sun was 5999K and 94.2 CRI
 
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eh4

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Re: Fun with a Sekonic C-7000 Spectrometer

This is neat.
I wonder if the less than 100% CRI of the sunlight comes down to limitations of the machine, or if a giant mass of hydrogen fusing into helium isn't a proper "black body", or if atmosphere and particulate are filtering out some wavelengths and reducing the CRI?
 

BVH

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Re: Fun with a Sekonic C-7000 Spectrometer

I'm not an expert but it seems from what I've read, that CRI is based on Tungsten filament lamps so a Tungsten lamp produces 100 CRI and all other light sources, including the Sun are rated against it.
 

BVH

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Re: Fun with a Sekonic C-7000 Spectrometer For Kelvin, CRI & Other Measurements of LE

Just in-case it was lost in the first post:

I would enjoy measuring lots of light sources for people if they send them to me. Send complete lights, bare LED's, commercial bulbs, whatever you might want measured. All it will cost you is postage. I have a commercial telecom grade programmable, current limiting power supply so I can power up bare sources so to speak. Example: LED's on stars as long as I can get a reasonable sized contact area or u attach wires to it. I can provide Kelvin and CRI/extended CRI measurements and, although I do not quite understand them yet, info on where the source is in relation to:

CIE1976
CIE1931(CIE1964)
XYZ
xyz
u'v'
λp (Peak wavelength)
λd (Dominant wavelength)
Pe (Purity)
PPFD
 

lampeDépêche

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Re: Fun with a Sekonic C-7000 Spectrometer For Kelvin, CRI & Other Measurements of LE

Very cool toy! And interesting that the sun in your part of the country reads reliably around 5.5k. Up here in the frozen north, I don't think it ever gets that cool/hot.

About the CRI readings being less than 100: I doubt that is anything other than ordinary variation in measurement. One half of one percent is pretty darn good for most devices, whatever they are measuring. I mean, *maybe* it's because of variation between the sun and incandescent tungsten. But there's also a decent chance that if you were to put this device in front of incandescent tungsten, it would also read 99.5 every now and then.

I hope someone will send you some of the Yuji 5mm LEDs. I am especially fond of the warmer-tint 3200K, and you might not like those esthetically. But it would still be interesting to see how they measure on a more sophisticated CRI measurement.
 
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