Spectral Graph - Quantitative Tint Comparison!

This is something I'm pretty excited about, I'm working on a crude spectrometer that can quantify a comparison of tint! A spectrometer basically takes light and splits it up into the different wavelengths it's composed of, showing you the full spectrum. This lets me see the difference between tints, because I can measure just how much of each wavelength is in the light. A warm tint will have more on the red end of the spectrum, and a cool tint will have more on the blue end.

This is a quick comparison I made to demonstrate this concept, between a Cree XM-L cool white and warm white LED (cool from a V11R and warm from an E03):


White: Cool White XM-L
Red: Warm White XM-L
Yellow: Difference

As you can see, the cool has much more blue, and the warm has much more on the red end.

There is definitely a lot of value to comparative beam shots to show tint differences, and this won't replace those, but this will take out a lot of the subjectivity and variance from things like camera settings, ambient light, monitor settings, etc. This has me pretty excited!

I like it...

I like it too! Very good idea and very interesting not only for tint but for colour rendering as well! Now the only thing missing from your reviews is a luminance and candlepower measurement! :thumbsup:

dimak said:

I like it too! Very good idea and very interesting not only for tint but for colour rendering as well! Now the only thing missing from your reviews is a luminance and candlepower measurement! :thumbsup:

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Yes, color rendering is definitely something I've had my mind on here! The math is that would go into calculating a CRI from a spectral graph like this looks to be pretty intense, but luckily I like math . As far as my reviews go, I could go ahead and convert my measurements to lumens, but I don't feel confident that I have enough data points to make a reliable conversion factor. Currently my accuracy is in the range ≈8%, which isn't good enough by my standards, so I'm not going to publish it yet. As for candlepower, I think lux seems to be what most people are using now (candlepower seems to have gone out of style), and I'm working on a setup to get precise and accurate lux measurements.

+

Interesting

~ please include tint codes or K degrees,... because warm can mean many things

orbital said:

+

Interesting

~ please include tint codes or K degrees,... because warm can mean many things

Click to expand...

You're right, it certainly can. I'll see if I can look those up. I know I've seen the tint code for the warm Xeno E03, but I'm not sure if Sunwayman has published the tint they use in the V11R. Right now, this is mainly just meant to show off what I can do so far, and get suggestions on possible uses for this kind of data. I'm already thinking of color temperature, tint, and color rendering.

I wish I still had access to a spectrometer =\

ah, well.

I'll hop into this thread with a FYI:



3000K High CRI Cree, ________________6500K CW Cree.




Ocean Optics Spectrometer.

Craig

0dBm said:

What measuring instruments are you using?

Click to expand...

The measuring instrument is an HD webcam, with a DVD for a diffraction grating. Like I said, a crude setup

But it's great for guys like me who don't have an extra $10k laying around :thumbsup:

Sent from my mobile device. Please excuse brevity and typos.

csshih said:

I wish I still had access to a spectrometer =\

ah, well.

I'll hop into this thread with a FYI:

3000K High CRI Cree, ________________6500K CW Cree.




Ocean Optics Spectrometer.

Craig

Click to expand...

Thanks for your input!

Sent from my mobile device. Please excuse brevity and typos.

orbital said:

+

Interesting

~ please include tint codes or K degrees,... because warm can mean many things

Click to expand...

From Xeno's website:


So the warm is somewhere between 3600K and 3700K. I'll see if I can get something more specific.

Ok, according to the Xeno marketplace thread, the warm tint is 3300 K.
http://www.cpfmarketplace.com/mp/sh...-(CW-NW-WW!)&p=2658684&viewfull=1#post2658684

I've sent a PM to Sunwayman to find out the tint bin of the V11R.

Very interesting...I'm still an advocate of warm lights, the only reason I haven't purchased a thrower is because most of them don't have warm versions.

Interesting results and a nice idea. But as we can see, your graphs are pretty different from the graphs given in the data sheets, and pretty different from the ones given by csshih too (measured with a real spectrometer). For example, three distinctively separate spikes instead of two. Are you sure about the accuracy? What kind of setup did you use for the webcam? A white box/sphere?

The graphs are clearly different, but they represent the two extremes (3300K and presumably 6000K+). Due to that, I would have expected even bigger difference (especially in the 450nm spike). I believe we might need more accuracy and precision before we could reliably compare, say, two manufacturers with the same CCT.

Anyway, a nice project. Looking forward to see more measurements.

jcw122 ^

Throwers are a different breed.
You truly get more punch w/ throwers using cool tints,,, 20% easy.

They just tear through the night sky :devil:
>>> This is the only time you'll hear me say anything positive about cool tints.

Bigmac_79 said:

The measuring instrument is an HD webcam, with a DVD for a diffraction grating.

Click to expand...

I wonder if that's where the third peak is coming from? There are twice as many green receptors as red or blue. That's why half of all dead pixels on cameras that aren't black are green.

jcw122 said:

Very interesting...I'm still an advocate of warm lights, the only reason I haven't purchased a thrower is because most of them don't have warm versions.

Click to expand...

orbital said:

jcw122 ^

Throwers are a different breed.
You truly get more punch w/ throwers using cool tints,,, 20% easy.

They just tear through the night sky :devil:
>>> This is the only time you'll hear me say anything positive about cool tints.

Click to expand...

Agreed that cool tints have more output, though I've heard people say that warm tints don't catch on fog/dust particles in the air as much. I haven't tried a real comparison to test this. I'd like to see a warm thrower, just to see what it's like.

AnAppleSnail said:

I wonder if that's where the third peak is coming from? There are twice as many green receptors as red or blue. That's why half of all dead pixels on cameras that aren't black are green.

Click to expand...

Well, the spikes are in the right places, but if the program is at least reasonably good, it shouldn't make that kind of mistakes...

Esko said:

Interesting results and a nice idea. But as we can see, your graphs are pretty different from the graphs given in the data sheets, and pretty different from the ones given by csshih too (measured with a real spectrometer). For example, three distinctively separate spikes instead of two. Are you sure about the accuracy? What kind of setup did you use for the webcam? A white box/sphere?

The graphs are clearly different, but they represent the two extremes (3300K and presumably 6000K+). Due to that, I would have expected even bigger difference (especially in the 450nm spike). I believe we might need more accuracy and precision before we could reliably compare, say, two manufacturers with the same CCT.

Anyway, a nice project. Looking forward to see more measurements.

Click to expand...

In short, no, I have no estimate of the accuracy. As I said at first, this is a crude spectrometer. I just put it together yesterday, and was too excited to wait to show it off . The webcam is currently inside a black box. A white box would reflect the light around too much, when I want the scattered light to be absorbed and not interfere with the new light coming in.

I've done a little fine tuning and now I'm seeing bigger differences than before, but still not as big as I might expect. I think it may be partially due to the nature of measuring the emitters from inside a reflector. I've noticed on several lights that the warmer tints tend to get thrown to the middle of the beam, while the cooler tints tend to get thrown to the outside (the reason for sometimes seeing a blue or pink ring around the edge of a beam). All my measurements were done towards the middle of the beam. Also, while the V11R is definitely cool, it doesn't seem to be extremely cool. It is still pure white, no hit of green or pink or blue (except a little blue around the edge as I mentioned). You can see what I'm talking about in this picture from my review:



Also we have to keep in mind that a certain color temperature refers to a broad range of possible tints. This picture illustrates what I mean:



As you can see, an emitter could be rated at 6000K and be either very green or very pink, which would show up very differently on a spectral graph.

AnAppleSnail said:

I wonder if that's where the third peak is coming from? There are twice as many green receptors as red or blue. That's why half of all dead pixels on cameras that aren't black are green.

Click to expand...

I had thought of that, and I'm thinking of some way to try to accurately measure the spectral response of my webcam to account for any errors there. However, my webcam in general does a pretty good job of showing things how I see them, so it's response must be pretty close to that of the human eye.

Esko, thanks for that link to the info on camera sensors, I'll read that as soon as I get the chance.

Thanks for all the feedback, you are all being very helpful!

Well, you were talking about a 8% accuracy in post #4... I was thinking it might be a white box, because with multiple reflections the possible tint differences in beam would be pretty much eliminated (mixed).