Convert X,Y values to Hue and Saturation or RGBW

[Pascal Steinhaeusser]

Hello,

I was wondering if any of you would have a link to a converter/calculator or a quick way to match x,y coordinates to Hue and Saturation or even RGBW?

For example, if there is a color I like in x,y mode on a skypanel but would like to match that color to another rgbw light that has only a Hue and saturation mode to change colors, how can I convert the x,y coordinates of my skypanel to hue and saturation so I can dial it in my other LED and colors of both of my LED lights would match or at least be of a really close match?
I would also be happy to know if theres is a way to translate these x,y values to RGB...

I've been doing a lot of research although websites I found became really mathematical and I would like to know if there is a simple way of explaining it or if there is a calculator out there which would make it way easier.


What I found until now

http://colormine.org/convert/yxy-to-hsl (Doesn't help so much because I do not know what value to enter in "Y1" and as a result HSL is too much info to put in a light. What I mean is you can only input Hue and saturation on a light not the "Lightness")

I would also have the possibility to get a new Sekonic c800 that seems to be giving you all the needed values in a readout. It would answer the question of this thread although I would like to avoid paying 1600USD for now. My point being if this tool is able to do it, there must be something somewhere on the internet able to convert color modes.

Thanks for your help!

 

[Phil Holland]

As there's really no standard being deployed by manufacturers when it comes to RGB lighting and also the variance found between RGBWW, RGBW, and RGB sources your best best is going to be the color meter in terms of physically matching the hue, saturation, and intensity.

 

[Michael Tiemann]

The CIE 1931 space is an absolute space. HSL is just a function of whatever you happen to have in terms of R, G, and B sources and how much you are willing to believe that equal magnitudes of R, G, and B add up to W. Not all red LED sources are, in fact, the ultimate red of the CIE 1931 space, nor are they necessarily the red corner of any well-established gamut within that space. Ditto green and blue. Kudos to ARRI for attempting to create an objectively measurable color from their light sources.

Note that the concept of "white" in the CIE 1931 diagram is really a path that depends on color temperature:

In the HSL world it's conventionally H = 0, S = 0, and L however bright you want it to be. Good luck finding the math that maps any point on that line to a truly correct HSL interpretation!

As Phil says, a color meter is the way to really match source colors (and to analyze the integrity of whatever the color reading may be--not all yellows or greens or purples are created equal!).

 

[paulcurtis]

You may want to review this

http://www.brucelindbloom.com/index.html?Math.html

You may find what you need here but i have no idea whether Arri X and Y are based on anything standard, but worth a shot

cheers
Paul

 

[Pascal Steinhaeusser]

Thank you all for your answers.

I've looked into it a bit more. Although matching different light sources will never be perfect cause of different manufacturers, quality, etc... I've found a solution that brought me close enough to some result. Not perfect but close matches. The greatest and most efficient solution is still the colormeter but I will share my findings here anyways:

You will need the website I linked in my first post: http://colormine.org/convert/yxy-to-hsl

Now I read somewhere but unfortunately I can't find the website to quote anymore: "Given X an Y, finding Y1 is straight forward because X+Y1+Y2=1"
For example: My given X,Y Coordinates are X=0.3320 and Y2=0.3500 ---> X+Y2 = 0.682 ---> 1 - 0.682 = 0.3180 which in percentage is 32% (because the website I use needs a value from 0 to 100 on Y1.)

Now enter numbers on the website:
Y1 = 32
X= 0.3320
Y2 = 0.3500

Results in HSL will be:
H = 39
S = 9
L = 58

You don't need the L value because you want to be able to enter the brightness you want.
By testing it with a Skypanel and trying out different values on X and Y, I found that the results were always a very close match in color to the equivalent of HS.
You can try it out. Enter random values into a x,y mode on a Skypanel. Do the easy math and use the website after to get your HS. Enter those HS values into another light that has HS mode (Quasar Rainbows I think) or if you don't have another light, try it in the HS mode of the Skypanel. Toggle between x,y mode and HS mode of the Skypanel and you will see the color looking quite the same.

Cheers