I'm guessing that's exactly his point!
Originally Posted by Dan Henderson
But if he's really doing a 4 hours exposure, at an f-stop small enough to make the background need 4 hours to expose properly, those people are going to have to be moving very slowly, and/or carrying some exceptionally bright lights, to get them to show up well also. I've seen pictures along these lines before (but never 4 hours long!) and the effects you can get are pretty neat. I can't wait to see the results here.