I recently bought a Leica 28mm Elmarit-R 2.8 ROM (Latest version) to use with my Canon 5D Mark II. After reading so much about the incredible performance of this lens I decided to get one for my Full Frame DSLR. So many people claimed that it was sharp corner-to-corrner even at large apertures. Unfortunately, this was not my experience. I found that the corners are considerably unsharp and soft even at f/5.6. They finally improve at f/8 but are not, "sharp". If anyone out there has this lens and a Full Frame DSLR, I would very much like to hear a contradictory report from them. However, if they take a photo - preferably of buildings - at f/5.6 or f/8, focused at infinity, they will be equally surprised and disappointed if they look at the corners at 100% magnification. I would really like to be proven wrong.