How did New Horizons take such well-lit pictures of Pluto? The photos of Pluto from New Horizons are truly beautiful.

But considering that Pluto is so far away from its nearest start - our Sun - how is it so well lit up? 

Did the New Horizons have a massive flash mounted on its camera to illuminate the planet or is there just a lot of ambient light in space? 

I'm really curious.
It's brighter on Pluto than you think.

NASA developed a tool called Pluto time, which tells you when at your place the ambient light conditions are similar to the ones on Pluto.  This occurs when the Sun is only 2° below the horizon!  That's quite shortly after sunset, and considerably before the end of civil twilight, which is when it's 6° below.

All of these photos were taken at local "Pluto time":


Pluto time, according to NASA.  Source: NASA

To answer your question: all it takes is a slightly longer exposure time / larger aperture / higher gain (what photographers may call ISO) than taking photos closer to the Sun.  It's easily bright enough for outdoor activities (except perhaps on a cloudy evening and/or in a dense forest, but neither should be common beyond the orbit of Neptune), so have fun glacier hiking on Pluto!