Approximating color temperature with smart phones and camera

That’s just a spreadsheet plotting those xy coordinates.

edit: you could also check out Osram Color Calculator.

but i only see those coordinates in the spotread output not in the spectrum file it saves

I usually just take a single measurement and log the data by piping the output to a file, because spotread doesn’t save all the data in the log. Or just copy and paste the text from the command line window. After first calibrating, use whatever parameters and -N -O > log.txt

Is it likely that the accuracy is device dependent?

This free program Osram ColorCalculator is super cool. I re-arranged the spectrum data into a CSV and imported it:

Here is a SST-20 3000K on high with a frosted optic

CIE plot:

R-value plot:

Some report like babel shows:

The actual program window:

Can somebody tell me how to calibrate the colors on a projector connected to one of those stupid fruit-branded all-in-one desktop computers? At our church, the media computer is a Mac of some sort, a few years old. The projector is connected by HDMI over Thunderbolt, IIRC. The colors are horrible! Blues are over-saturated while reds are badly washed-out. I tried the on-board “monitor calibration” …thing on the Mac, but it only had brightness, contrast, maybe gamma, but no per-color-channel fixing. The projector itself has per-color-channel controls, but they don’t help, so the problem seems to be in the signal from the Mac! The LCD monitors connected to the Mac show colors “fine” though. Just the projector doesn’t. So, I don’t know what the deal is actually. Help?

I agree, it’s a great software for the price :slight_smile:

It seems their newest version also supports the TM-30-18 report format, which looks very professional. The latest CT&A also does that.

Does this mean high colour accuracy light source tint mixing isn't really detrimental to their overall CRI, TLCI and such indexes?

Monitor test patterns may be of help, try here for example: The Lagom LCD monitor test pages

Speaking of tint mixing you can enter multiple measurements and the program will plot an estimate for that too.

Unfortunately CT&A doesn’t appear to support the ColorMunki Photo, or at least i couldnt make it work

Good stuff contactcr! I like that a few more people on BLF have the opportunity to measure the colour information of our flashlights.

From the spotread documentation. I think this basically means any really rosy or green LED will always have the “caution” warning.

I downloaded the "White Balance Color Temp Meter" to my Pixel 3 and tried it out. Readings were taken on lower modes, in a dark room, with a sheet of printer paper as the backdrop.

Rovyvon Aurora A8 Olight S1R Nitecore TUP, LH351D mod FW3A (3D) Nitecore P18, XHP35 Hi swap Armytek Elf C2 (Warm)
Expected 5000 6000 5000 5000 4500 4000
Test 1 4600 5320 4660 4540 3810 3620
Test2 4510 5380 4440 4440 4300 3750
Average 4555 5350 4550 4490 4055 3685
Difference -445 -650 -450 -510 -445 -315

I have no source for the Elf C2 CCT and guessed at the expected value. If I shift all the values up by 500, using the average of two readings:

Rovyvon Aurora A8 Olight S1R Nitecore TUP, LH351D mod FW3A (3D) Nitecore P18, XHP35 Hi swap Armytek Elf C2 (Warm)
Expected 5000 6000 5000 5000 4500 4000
Corrected average 5055 5850 5050 4990 4555 4185

These now fall within about 150K of the values I was expecting. Taking more samples would likely improve the consistency as well. Very promising!

I dont have any of these lights but the real measured CCT is never even numbers.

For example the Wuben with 5000K 90CRI LH351D: CCT = 4816K

So your numbers could already be closer than you think.

Yes, of course. I know, for example, those 4500K XHP35 Hi LEDs tend to measure cooler than advertised. I mostly want to be able to loosely quantify CCT for my reviews, and for that I think a 250K or 500K range gives people enough of an idea.

Most flashlights have a warmer hotspot and cooler spill. Averaged and integrated over the beam the results are usually spot on at binned CCT.

I might get a good price on a used xrite I1 Pro (looks like the one on the firsts pictures from OP as far as i can see)

Is that one still recommanded ?

Yes. It’s still good for LED measurements although the i1Studio/Colormunki Photo may be cheaper and practically just as good for what we do. I like the Babelcolor CT&A, which doesn’t work with the i1Studio.

That one was cheaper than I1studio /Colormunki Photo so i am testing it now :)

I see in the OP that you were using spotread with -a (ambient), was that with the I1pro ?

I am asking because despite having an ambient measurement cap with my I1pro, Argyllcms returns a "Requested ambient light capability, and instrument doesn't support it." error when i try to use the -a instead of -e

An other question : Do you use the ambient measurement cap (ref 609192) ? If i don't use it the sensor is easily saturated but when i try to use it the CCT seems to be off

If you run spotread.exe -v, what does it say?

The label says x-rite, eye-one Pro, rev D