Different meaning Color Temperature in Hue and Zigbee binding LTW001

Hi all,

thanks so far for all the support that I’ve got here it helped me a lot and I get better and better every day.

Today I’ve tried some comparison.
I’ve connected on LTW001 bulb to Zigbee and the other one remained at the Hue bridge.


The outcome was that the color temperature in reality is different if i set the Value in Hue or in Zigbee.

Here an example:

When I set the value in Hue to 50, I need to set the slider to 75 in the Zigbee binded device.

Is this normal? Does someone already have a formula to correct this?

Hue Zigbee
0 0
25 50
50 75
100 100

This is a short-coming of the 0-100% mapping of the color temperature. Unfortunately the absolute color temperature is not linked to the 0-100% in a fixed way. The mapping depends on the capability of each device and you need to find the corresponding values by trial-and-error.

As @J-N-K says, I guess the two bindings map the color temperature slightly differently. IIRC Zigbee maps it between the max and min values that the device reports and probably Hue does something different.

Ideally there would be a standardised type for this - I think this was discussed some time in the past but not taken up. An alternative could be a standard channel type with a standardised definition of what the mapping is, but again I don’t think that exists at the moment (unless I missed it :slight_smile: ).

The deconz REST API reports the capabilities of the device in mired, I guess this is directly derived from what the device itself reports. The deconz binding uses this for an absolute color temperature channel.

Even if I doubt that these are exact matches (I doubt that manufacturers calibrate their lights), this is most likely less than with the 0-100% approach.

Agreed - and we could never get around that short of adding some sort of software calibration. However having a standard would still get things 95% of the way there I expect.

1.) Different light bulbs have different ranges 2700k - 6000k or 2000k - 4000k
2.) Different bindings treat color temp in differnet ways kelvin or mired

You could map 0% - 100% to the real color temperature values

Again though, while there are lots of different things that CAN be done, unless there is a standard way to do this, each binding will inevitably do something different, and I guess that was the basis of the original question.

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Hi all

just an idea could the Mapping of OpenHab simply be how many percent the bulbs are actived.

0 = Only Blue
50 = Blue + Red
100 = Only Red

But okay I understood that this value might be calculated by Hue itelf which is not a too big deal.

With the fact that the red light is not so bright it’s interpolated…
I put in a Formal like this and came to a similar (not identical) result.

And here in openhab.

The Zigbee standard, which Hue uses, defines how to set the color temperature so it’s not a case of the bindings trying to calculate RGB valuies for color temperature.

The issue here is how the bindings are mapping the 0-100% to the color temperature - what is 0% for example - this isn’t defined so we end up with different settings per binding.

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From my view it is even more complicated. If i remember it right than the hue binding handles hue bulbs like 0% - 100% equals 2007k - 6000k and if you use a ikea tradfri bulb it is the other may round like 0% - 100% equals 6000k - 2700k

Yes, so that’s exactly what I said - it’s just how the 0 to 100 is mapped and it’s not defined anywhere. It’s not really related to the standards - just how bindings present them.

Tradfri and Hue both use Zigbee, so at the “bulb” level, they are the same - so if there’s a difference then again this is the binding.

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