RGBW light color correction through max_power has no effect

[baracoder]

Operating environment/Installation (Hass.io/Docker/pip/etc.):

docker

ESP (ESP32/ESP8266, Board/Sonoff):

"MagicHome" LED controller with esp8285

ESPHome version (latest production, beta, dev branch)

v1.15.3

Affected component:

light rgbw https://esphome.io/components/light/rgbw.html output config https://esphome.io/components/output/index.html#config-output

Description of problem: An RGBW light strip has blue tint. Color correction refers to setting max_power for individual outputs to correct. Setting different values does not affect light color, when setting rgb to white through home assistant.

Problem-relevant YAML-configuration entries:

output:
  - platform: esp8266_pwm
    pin: GPIO14
    id: pwm_r
  - platform: esp8266_pwm
    pin: GPIO5
    id: pwm_g
    max_power: 0.85
  - platform: esp8266_pwm
    pin: GPIO12
    id: pwm_b
    max_power: 0.7
  - platform: esp8266_pwm
    pin: GPIO13
    id: pwm_w

light:
  - platform: rgbw
    id: strip
    name: ${upper_name_1}
    red: pwm_r
    green: pwm_g
    blue: pwm_b
    white: pwm_w
    default_transition_length: 300ms

Logs (if applicable):

[D][light:287]:   Red=100%, Green=85%, Blue=71% <-- used those values for calibration
[D][light:287]:   Red=100%, Green=100%, Blue=100%  <- set to middle of color wheel in home assistant

Additional information and things you've tried:

[CarlosGS]

I had the same problem, now adding a note to the documentation https://github.com/esphome/esphome-docs/pull/742

Remember that gamma_correct is enabled by default (γ=2.8), and you may want take it into account for the calibration. For instance if you command a light to 50% brightness and want it to be the new maximum: max_PWM_power = max_light_power^2.8 = 0.5^2.8 = 0.144, then you would set max_power to 14.4%.

Also note that ESPHOME is always going to report the command scales from 0 to 100%, max_power has its effect internally.

In your case, when the blue channel is set to 100%, internally it sends 70% of power. That is not a perceptible difference due to gamma correction. For that channel you should be setting max_power = 0.7^2.8 = 0.368. Sounds very low, but that's how light perception works. Cheers!

[lambdahindiii]

I had the same problem, now adding a note to the documentation esphome/esphome-docs#742

Remember that gamma_correct is enabled by default (γ=2.8), and you may want take it into account for the calibration. For instance if you command a light to 50% brightness and want it to be the new maximum: max_PWM_power = max_light_power^2.8 = 0.5^2.8 = 0.144, then you would set max_power to 14.4%.

Also note that ESPHOME is always going to report the command scales from 0 to 100%, max_power has its effect internally.

In your case, when the blue channel is set to 100%, internally it sends 70% of power. That is not a perceptible difference due to gamma correction. For that channel you should be setting max_power = 0.7^2.8 = 0.368. Sounds very low, but that's how light perception works. Cheers!

I had the same problem with RGB light and was struggling to figure it out. This solved it for me completely. Thanks!

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