While working on a review I came up with this idea to measure the color temp of LED's using my camera's manual WB setting, here's the excerpt:
TINT
I decided to try something a little different this time around by grabbing one of these from my local Home Depot to help with getting a good idea of the tint of a common object illuminated by the X60L:
My camera has the capability to adjust WB by Kelvin (betw. 2.5K - 10K). This forces the camera to apply a white balance using your input as the baseline temperature. If what you've input is lower (warmer) than actual temp, the picture will come out cooler and if above (cooler) then the pic will come out warmer. Using this feature, we can get an idea of the color temperature by what the final setting was before the "Polar Bear 1875" (1st row, 3rd column from left) turned truly white. In the control shot above, I used the camera's custom white balance setting under fluorescent light so it's pretty realistic to what my eyes see.
I used the following three color temps as a baseline and what the type of color it is representative of in real life:
2800 - 100W Incandescent bulb
4800 - Direct Sunlight
10000 - Blue Sky
Here is the control sheet shot w/the above settings respectively (also under fluorescent light) from L to R (2.8K | 4.8K | 10K):
As you can see, the color temp runs from cool to very warm (since the particular fluorescent light I have is a bit on the warmer side). Given I forgot to take the ideal sweet spot for this pic, we can however estimate that my fluorescent light falls between 2.8K to 4.8K.
Now here is that same sheet but illuminated on High by the X60L:
Taking a look at the above, 2.8K is obviously too cool, while 4.8K comes close and 10K is too warm. As such, you know the temp of the X60L should fall somewhere between 4.8K and 10K (but closer to 4.8K).
I finally got to what I thought was in the ballpark for the Polar Bear to be white and this was taken at 6.8K:
But as you can see, Polar Bear white has just a hint of bluish tint in it so I'd say final ballpark would be roughly 6.5K.
By comparison, here's a light that has a neutral XM-L 3C tint:
Let's go through that drill again, 2.8K? Nope, too cool. 4.8K - wow pretty close! 10K, nope too warm. In the end, 4.8K (likely closer to 5K) was closest to turning the Polar Bear paint pure white.
Obviously it's no Spectrometer but great for comparative purposes and to get a rough idea of the color tint. If your camera has this feature, it's worth giving it a shot. It doesn't have to be the palette above and can be any old white sheet of paper.
Cheers,
Tim
Nice. Why don't you just adjust WB until you get pure white? Or does your WB only have discrete settings?
I also thought about using the metering of the camera to measure brightness but haven't figured it out yet.
I could've but it just looked so boring... besides that's what white wall shots are for. ;o)
But in all seriousness, as I mentioned, it doesn't have to be that color sheet, it can be a plain ol piece of white paper.
This reminds me that quite sometime back,I have measured colour temperate of the some LED I bought by using my wife camera. You can manual set the colour temperature as mentioned by turboBB and or use the custom set function on the white balance menu on the camera to determine the CT of the surrounding in this case the CT of the led. I don’t have CT meter or clourimeter( pretty expensive stuff) to compare with.but the results I get are quite positive. For example,Tested it on h600w rated at 4200k.on lowest, 4000-4100k and high to turbo 4200-4300k.more testing to be done when i have more spare time to determine if using a camera is a good method to test LEDs CT.
Really good write up and pictures! thanks for the opportunity to learn even more.