Hi Sanders - OK, got it. You are not looking for a practical answer, but a theoretical one... So, you have this backwards. The lens that is closer to it's optimal design speed should, all things being equal, be "sharper" (your original question) than the faster version stopped down; it should have less flare and better resolution. So the slower lens should be superior to the faster lens stopped down to the slower lens' full aperture speed... Eric Goldstein On Mon, May 6, 2013 at 3:51 PM, Sanders McNew <sanders@xxxxxxxxx> wrote: > > > I'm asking an equally-theoretical question, to test your hypothesis. Is > it not true that taking a faster lens > and closing it one stop will produce a superior image (as respects > resolution) compared to the lens shot > at its full aperture? snipped) >