iPhone: What is the maximum luminous intensity of the front and rear flash (screen flash)?

The title of the question says it all, I've been looking through the specifications, however I could not find information about the brightness of the back and the front flash for an iPhone 6 (front flash emulated by increasing the brightness of the screen). Specifically, I am interested in the maximum intensities for both the rear and front flash.

Is it available somewhere or has it been measured by someone?