He's run real tests using IMATEST and the results are interesting: The site is about lenses for shooting coins. Just now, I've discovered a site () with tests of a number of lenses from 1:4 to 1:1 and beyond. A few lenses are optimal at 1:1 (my favorites: 75mm APO Rodagon D 1:1, Olympus 80mm bellows lens) Thus, they make great macro lenses reversed for say 5:1, but not optimal at 1:1 Enlarging lenses are designed for typical print sizes. Much better than 'normal' lenses, but not optimal at 1:1. Macro lenses are best at 1:3 or 1:5, even though they may focus to 1:2 or 1:1. You can focus close with tubes or bellows, but the performance is compromised. Most lenses are designed for normal shooting distances, not macro. Lenses are optimized for a certain range of magnifications (image:subject conjugates) The common wisdom I've accumulated about lenses in this range over the years: Also for slide copying and digital-camera-as-scanner. I've been especially interested in shooting at around 1:1 for flower center details, insects, etc.
I've been using and reading about macro lenses for years.