Sandy ... is there some type of factor or estimate for getting the estimated "full" image circle compared to what is published by the manufacturer at f-22? The Fuji 360mm that I have at the top of this thread has an image circle at 485 at f-22. What might I expect the "full" circle to be? What type of shutters might limit the circle? Is that called mechanical vignetting? Are the Copal 1 shutters less prone to this due to their larger size?