Well, the three times there make about a second for one light-change. So let's say it makes two light-changes, to be sure, for three images (it does say "multip

Well, the three times there make about a second for one light-change. So let's say it makes two light-changes, to be sure, for three images (it does say "multiple images", not "two"). That's two seconds, and then say there's another second for processing. Not too unreasonable, especially if (as it says) single-image systems also take about three seconds overall.