How to measure temperature of my video lights precisely?

[Pearlman]

Hi Folks
So I want to experiment with many different WB settings than native with my Gopro and the results with post-processing. Like 4500/5500K and observe how my color grading results look. I use a red filter UW FYI.


I have some video lights that use CREE XM-L2(U4) LEDs. Checking online (https://www.cree.com/led-components/media/documents/ds-XML2-EZW.pdf)I see many variations in color temperature.

Rather than spend hours going through online docs I am looking for a simple common sense practical way to measure the WB Temperature of these lights using a camera and some post-processing software - I have DV Resolve and Aftershot Pro installed.

Anyone know how I can do this? Any caveats - like is my monitor Gamma setting also relevant in estimating this?

Thanks

 

[Pearlman]

Problem solved - I found a Lux meter app on Android Playstore that gives a color temp reading!

 

[kelemvor]

For underwater, you probably want to get a "grey card." They are sometimes described as 18% grey. You take a pic of it (or just put it in front of the camera if video) when you start filming. Then when you're processing the photo or video, you sample the photo of the card for white balance. You can get a grey card just about anywhere for a dollar or two. Just make sure you get a plastic one for diving. https://www.amazon.com/s?k=grey+card

For land based stuff I use a Spyder Cube which has several surfaces allowing you to adjust more than just color balance. Datacolor SpyderCUBE RAW Calibration Tool

If you really 100% must measure the output of your lights, then you can get a colorimiter. They start at about $250 from what I can tell on Amazon. Also, a monitor colorimiter is AWESOME for tuning the screen of the computer you're using to edit photos. Night and day difference between a calibrated and uncalibrated screen even if it's not a high-end photography panel.

I don't have a colorimiter that would be suitable to test a light. I use my grey card or cube for that. I do have a colorimiter for my monitors.

The problem with using a phone app is that the phone camera needs to be calibrated just like your gopro, your Nikon D850, or your RED Epic.

 

[bvanant]

It all depends on how accurate you want to be. A good Sekonic color temp meter is like $1500, other versions can be $600 or so. Good lab spectrometers are a lot more (Thorlabs etc.)
For "good enough" you can use the Cine Meter II app ($25) which is quite accurate if you cal it for wide band illumination. If you are serious you can get a LuMu lab attachment ($250) for your phone that is really nice.
Bill