I think my brightness is just fine - I have no problems whatsoever reading my phone outside.
I just use the toggle widget to toggle it up to the highest brightness level (actually, whatever the highest level is on the toggle - I don't know if that's full maximum brightness or not) and to me, it looks just as bright and vivid as it does on the lowest brightness inside. To me, at least. Now, I can definitely have problems seeing if I forget to toggle the brightness, but as soon as I do, it's just fine. In fact, it's more than fine, it's still beautiful!