How bright are the outer planets, when at close range? Seven probes have passed by or orbited outer planets. I wonder how their photos differ from the naked eye view one would have if one were actually there.

Saturn is 10 AU from the Sun, which means that it has just 1% of the sunlight we have on Earth. Would an astronaut orbiting Saturn, looking out of the window, even notice that Saturn is there? A clouded winter night on Earth can be really very dark, so you can't see where you put your foot while walking. But the outer planets at least have star light and a wage glimpse of the sun.

Can the light conditions out there be compared to a clear night on Earth with a full moon, half moon or new moon?
There is a rule about average surface brightness: it is conserved as you change distance or magnification.  For the gory details see.  Telescopes make unresolved objects brighter, but for resolved objects, a telescope shows you the actual surface brightness (assuming that the exit pupil diameter is well matched to your eye's pupil (~7mm) and is not throwing away light, dimming the view).   The surface brightness of any resolved object through a telescope is the same as it would be if you were there.
Also, the 0.01 of earth sunlight received at Saturn is way more than the lighting provided by a full moon which is 400,000 times fainter than the Sun.
What you also need to take into account, is that when you look at Saturn through a telescope, it is generally (not always) done at night when your eyes are dark adapted.