I don't have solid numbers, but I have been using several devices, including the Air 2 and iPhone 6 outside in direct daylight quite a bit lately, and I think the Air 2 is very usable in such conditions - it is bright enough, and the anti-glare filter is quite effective here. I think it's better than the iPhone, and miles better than several competing devices that I've seen used by coworkers under the same conditions. It's by far the best iPad so far for outdoor use.