We usually like to have control, but in this case Auto Brightness is the key
It's no secret that Samsung made some serious steps forward in display technology with the Galaxy Note 4, boosting resolution, colors and brightness to the highest levels we've seen from one of its phones. The 5.7-inch QHD display is quite gorgeous in any setting, and the bevy of display modes in the settings helps you tune it to you liking. But the most mundane of settings, Auto Brightness, is one that you want to have checked if you plan on using your phone out in the sun.
It may seem counter intuitive to have Auto Brightness checked when you're outdoors as you'd prefer that the display is always at 100 percent in bright sunlight, but it's best to trust the phone's software in this situation. When you're outside and the sun is hitting the phone directly at a high enough level, the Note 4 will go into a completely maxed out brightness mode — jumping up to 750 nits, over the standard max of 500 nits — to make the screen viewable in even the brightest situations.
This 750 nit brightness mode is so bright and uses so much power that it isn't accessible as a standard mode or setting, so the only way to let it activate is to use Auto Brightness. When it kicks in you'll notice a dramatic increase in brightness on the screen, so much so that the colors on the display also wash out a bit as a side effect. But for most folks that's a worthy trade-off to be able to see the phone without shielding it from the sun.