Ken I have done the side-by-side test with three lenses: a 180 Apo Sironar N/180 Macro Symmar HM/Apo Macro Sironar S. I measured my magnifications carefully on the rail of my Horseman LS and right up to just a few mm shy of 1:1 there was no discernible difference between the three lenses. The moment I hit 1:1 the differences between the macro lenses and the standard 180 were clearly evident, especially as you moved toward the edges and corners of the image. The test subject was a long silver necklace made up of thousands of small (2 mm across) links and it was heaped to check both depth of field and resolution.