According too Phil Schiller in the keynote speech, iPad Pro is 25% brighter than an iPad Air 2 and puts out 500 nits of light. It's the brightest tablet available.
By the way, if you're like me and have no earthly idea what a "nit" is, I'll save you the trouble of looking it up. A nit is a unit of measurement of luminance, or the intensity of visible light, where one nit is equal to one candela per square meter. Nits are used to describe the brightness of computer displays, such as LCD and CRT monitors. [Source:
Webopedia]