After the 1.4.2_0069 firmware update some lighter RGB colours lost a lot of brightness from my v1 bulb. For e.g. I have matched an incandescent bulb with rgb(255,160,70) (16752710 for the set_rgb command) because the 2700K colour temperature wasn’t the best match, however the brightness of the incandescent bulb, the RGB and the CT mode were the same (at 90-100% brightness value in the app). After the firmware update in RGB mode the max. brightness faded to about 60% of the original. In CT mode (2700K) the brightness remained the same.
After the disastrous update I have reset the bulb and re-added in the device list but the brightness loss didn’t change, so it’s in the new firmware.