DIY spectrometer

In trying to obtain some objective ways to evaluate different light sources, I find there several ways to build a spectrometer with as little as a usb webcam, a scrap of DVD disk, and a simple enclosure. Apparently, software is available free but I have not downloaded it yet. For more info, google “DIY spectrometer”

I’m not sure what you’re trying to accomplish? You can find the light spectrum of most sources pretty easily.

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I am trying to establish the “quality” of the output of “off the shelf” LED bulbs. By removing most of the bulb and lining the rest with reflective material, I have almost doubled the lumens, but more experimenting is necessary.
Simply viewing the light reflecting off an unused DVD, it is possible to get a rough idea of the spectrum.
Thanks for all the great info shared here. This site has become my “go to” source.


I have a interest in this because there’s so much false advertising in the light industry like this xyz light is the best 660nm spectrum out there it would be great to test it for your self to see if it’s true or not.


A spectrometer isn’t really going to measure intensity of light, just relationship of intensity of different wavelengths right?

Right, intensity is easy to measure, quality not so much.
Try this, view the light off an expensive LED by reflecting it off a DVD. Is there green? For my cheap bulbs the answer is yes, in approximately equal intensity of the blue and red. If green is of no use in photosynthesis, then 1/3 the power is being wasted. I would like to go a little farther and quantify the spectum a little more accurately.

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Oh my, there’s so much you’re missing. What’s color temp and cri of your bulbs? A 3000k 80cri light spectrum is going to be pretty close to the same regardless of who makes it. Just by the standard in which they are measured. For the purpose you want, a simple web search can provide you with information that’s accurate enough to avoid green light if that’s what you’re looking to do.

If you believe that green light isn’t useful, there’s literally hundreds of products available that can do that for you. However, I would strongly consider visiting NASA or Oxford’s lighting documents before doing so.


I started this thread because i found something on the web that I thought might be of interest to others, now I feel like I’m defending a position. This is going in the wrong direction.

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neat topic @roaddog love the dvd idea and can’t wait to look at lights reflected in it. keep questioning, searching, and researching!

Sorry about that. Perhaps i was confused in what you were looking for, carry on.

An interesting video on the subject:

For the McGyver in all of us: