I always use auto brightness for my laptop, but I find it sometimes too bright to me. And in Windows, the backlight adjust curve is smoother than that in Fedora (I mean, for example, while in 30% or 100%,Windows and Fedora will have the same brightness, in 70%, my screen is much brighter in Fedora). I guess the reason of too light with auto brightness may be related to a less smooth backlight adjust curve.