Light Calibration (dimming curves, ranges): make lights consistent

[chefdeit]

Describe your core improvement

One LED bulb's "10% bright" may look more like 30% of its max output compared to another bulb's 10% bright. This is because different manufacturers implement light drivers differently and pay different mind to the human eye's logarithmic perception of brightness range.

I'd like to be able to:

1. Define a HA-wide brightness curve preference, where an admin can, for example, allocate more of a UI's brightness slider's range for the end-user to be able to dial in the lower brightness levels more precisely.
2. Define one or more "template calibrations" so that one can be assigned to any light fixture or bulb in HA. This template would map the lowest available stable (hiss / buzz / flicker-free) starting output light output level from the fixture to its corresponding "raw/uncorrected dim %" input level. To speed up and simplify math, it would also map a few standard points, such as 2%, 5%, 10%, 20%, 50% light output levels to their respective "raw dim %" dimmer input levels. Free mobile light meter apps exist to help end-user measure. It'll be good if these calibration profiles could be shared similarly to blueprints. (For RGB lights, they ought to apply to individual channels - and would help them track neutral output better through dim% range and across fixtures).
3. Optionally, also be able to cap the individual light's output to less than 100%. Not sure if it's better in UI to show the capped value as the "fake new 100%" or to actually gray out part of the disallowed range at the top, similar to unavailable rang eat the bottom where a given LED is unable to glow at say 0.4% brightness level (1/256).

Once calibrated, the dim % you ask for becomes the light output % you actually get, across all fixtures. Different RGB or RGBCCT color lights' colors actually match. And no worrying about the buzz or flicker or overheating.

Current limitations

Illustrating the issue by way of a worst-case example, a given dimmer and/or the light itself may hiss or buzz badly in say the 0-5% dim level (electrical input). A fixture doesn’t light up at all in the 0-3% electrical input range. It lights up at say 3.1% dim level (lighting up right away at 7% of its max lumen output level) but besides hissing is also flickering. The flickering goes away at 6% dim (electric input) level, at which point the bulb is producing 11% of its max lumen output level.

Aside from the shenanigans at the low end of the brightness range, at the high end the user may want to cap the max output level at say 85%, for reasons of extending hard-to-reach bulb life or avoiding hitting installation-specific thermal constraints.

Right now this can be "sort-of handled" by hard-coding specific light levels into specific scenes, but not in any clean way with automated dashboards etc.

Technical benefits

Given the Home Assistant's mission to deliver a good user experience across an open and diverse set of consumer-level devices incl. dimmers and light fixtures, making their outputs more consistent through the dimming range will improve the Home Assistant user experience.

Additional context

Lutron's hospitality and luxury portfolio e.g. https://luxury.lutron.com/us/en/controls as well as similar premier ecosystems by other vendors, pay a lot of attention to harmonizing different lights throughout their light output range, and mapping that range to end-user's "% brightness" demand in a smooth and convenient way.

[Hugovdberg]

Another reason one might want to cap the maximum brightness is because a light might be too bright due to the way it's mounted. In my opinion the dimmer curve should be an attribute of the light entity, which defaults to a simple linear mapping (on top of the hardware scaling currently supported for integrators), but could be changed to either some exponential curve or even a piecewise linear curve as long as it is strictly monotonically increasing.

[roelanddewindt]

Akin to this, and a potential fix, is RGB individual channel calibration, see https://github.com/orgs/home-assistant/discussions/3538 to correctly reproduce Kelvin temperatures with RGB led strips and lights. This should happen at a very low level IMHO.

EDIT: wrong url

[chefdeit]

Getting a 404 at that link. But yes absolutely, and as I said at the end of Point 2:

(For RGB lights, they ought to apply to individual channels - and would help them track neutral output better through dim% range and across fixtures)

[roelanddewindt]

Updated above URL. We're talking about 2 different things here, but what you need (cap brightness per light entity) should be equally possible.

[chefdeit]

Thanks for the link!!
I'm not understanding re: 2 different things. Capping brightness per light entity is a small part of this request, asking for full calibration, incl per RGB channel.

[chefdeit]

P.S.: Your request has a lot of relevant technical specifics; it's very useful that there's now a link folks can follow to it.

[roelanddewindt]

About 2 different things. My first attempt was to write the code to control the color cast of my lights, so any Kelvin value would be reproduced in a neutral white (warm to cool) instead of the green or pink cast my lights produced. I thought this was done directly on the RGB values by HA. Only when I struggled to change RGB channels independently (see writeup), I found out that HA does not send RGB internally. It controls separate Xxy coordinates (color) and brightness, at least that's what it looks like.
When using XY I had much better control over the colour of me LED strips, and was able to achieve an acceptable reproduction of neutral cool to warm white light. Updated my code to also accept XY coordinates, see v0.0.2.
So color (XY) is separate from brightness, hence the "2 different things" reference.