An illumination device is provided having one or more illumination LEDs configured to provide illumination for the device. Along with the illumination LED is a reference LED. The illumination LED provide illumination during normal operation of the device, whereas the reference LED provides a reference illumination, but does not provide illumination during normal operation. A light detector can detect light from the illumination LED and the reference LED, and control circuitry can be used to compare light detected from the reference LED and the illumination LED to adjust a brightness for the device. The light detector can comprise a photo-detector or can comprise an LED, such as one of the illumination LEDs if more than one illumination LED is utilized. A method is also provided for controlling brightness of an illumination device.