It’s getting to the point where Photoshop creations look just as real as photographs now. Look at the train station and close-up of the train pics in this thread:
http://forum.ebaumsworld.com/showthread.php?t=131980
And that was over 5 years ago. I don’t think we can always answer the question in the OP if the artist is good enough Photoshoper without resorting to reverse-psychoanalyzing the artist (“If that’s photoshopped, why would he have made that bright spot there? why wouldn’t he have done it this way or that instead?”)