In a test of "tactical scopes", in Sweden. They had a good array of scopes, 4-16x50 Hensholdt, 5-25x56 S&B, 6-24x72 Hensholdt and a few others.

The 6-24x72 could keep on shooting at targets hundred of yards away, after the light was gone, and long after the others could not see a thing. I belive they stopped after 45 min, just becuase it was getting to cold for the other shooters to just lay there.

Objectice size matters.. it pulls in more light