What is the best process to use to work out the appropriate colour calibration settings?
The diffusion material on my jacket is a slightly off-white fur, and I think it’s that off-whiteness that’s making my whites look a little red. Is there a logical process to go through to work out the best way to fix this with FastLED’s colour calibration settings or is it just “fiddle around and see what looks good”?
I’d say fiddle.
There are other routes, but they involve color calibration hardware at this point – and it’s not clear to me that that’s actually better for this anyway.
In my future dream world, we could just run a sketch, point a webcam at it, and read out the numbers. But this world is not that one.
Usually when things look a little red it’s because you’re not getting enough power to the leds. Set the strip to full power while and if the first one one a strip and the last one are slightly different colors (with the last one more red) then it’s a power problem not a calibration problem. Many of my wearables exhibit this because of thin gauge wires and batteries and the like.
What Zeke said is also why, as voltage fades, the blue LEDs go dark first, then the greens, and finally the reds; red LEDs light at a lower voltage than greens, and greens lower than blues. (Mostly.)
Simple demo: get a “12v” led strip and power it with just 5v. The reds will light dimly, the blue and green not at all.
(Also a simple demo: get a 5v strip and power it with 12v. This demonstrates how to destroy a 5v strip quickly and easily.)
@Mark_Kriegsman Tried your last trick the other day, the LEDs survived, the Beetle driving them didn’t.
And in this instance it’s not a power problem, I’m getting plenty, it really is the slight beige tint on the diffusing material.
Speaking of color calibration hardware… As a compooter perfeshurnul, I have need to calibrate stuff and I use one of these: http://xritephoto.com/ph_product_overview.aspx?id=1115
Relatively cheap and can be used as a stand-alone spectrophotometer that can capture ambient and transmitted light.
I built a portable good-enough (8-bit :D) color meter from off-the-shelf parts… http://imgur.com/3NRJAH8
Used this $40 sensor…
…and of course I wound up rewriting their driver library… I’m not Bad, I’m just coded this way.
But you are just awesome… I am merely incompetent 
Well. Thank you. But let’s just say that while mine probably cost 1/8th of the professional one, it probably wasn’t even 1/80th as accurate!
(It was a fun project though.)