Philips Hue modes and circadian rhythm



  • I know F.lux supports Philips Hue. Does anyone know the difference between "xy" and "ct" mode? The LED bulb emulates sunlight i.e. what's known as 'correlated colour temperature' or CCT, however Philips says max range is from 2000 to 6500 K. But by using "xy" mode I can get beyond these limits.

    If I go below 2000 K, say, by typing [0.65],[0.34], will I really get the correspomding 1000 K? Or is this just some 'fake' colouring with no true effect on the body circardian rhythm?

    Just wondering...

    – celerity



  • @celerity well I can say that the red mode is truly all red. So around the 2309, 1900K looking colors, it should be fairly close.

    Use a greenish yellow in the color pick and go down from there. You'll find it.



  • What do you mean by 'truly red'? 1900 K (or 2000 K – no big difference) is not red but orange-yellowish. Max 'ct' input is 500 (500 mired = 2000 K). That's the technical limit of the bulb according to Philips.

    A CT-XY converter: http://www.ledtuning.nl/en/cie-convertor

    Here's what Philips dev says about different modes:

    We can also choose to address the color point of light in a different way, using colors on the black curved line in the center of the diagram. This is the line that follows white colors from a warm white to a cold white. hue supports color temperatures from 2000K (warm) to 6500K (cold) with great white light. To set the light to a white value you need to interact with the “ct” (color temperature) resource, which takes values in a scale called “reciprocal megakelvin” or “mirek”. Using this scale, the warmest color 2000K is 500 mirek ("ct":500) and the coldest color 6500K is 153 mirek ("ct":153). As with xy, the light will go to the closest value it can produce if the specified color temperature is outside of the achievable range.

    http://www.developers.meethue.com/documentation/core-concepts

    Still doesn't explain why I can go outside 6500-2000K using 'xy' mode. I noticed Philips sometimes talks about 'functioning white light'. Anyone know what this means?


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