According to Calumet, and I believe them, the current Caltars are the same glass as the normal Rodenstocks. They buy a quantity every year and have them made with their brand. The 6.8 is an excellent lens, as is the similar Schneider, sold as the "Classic." Unless you must have the extra speed, it is the best buy in a new 90mm. I have not owned one. I did have the Schneider 90mm f6.8, and now have the Rodenstock 90mm f 4.5. They both give first rate results. The 4.5 and 5.6 are a little heavy for traveling, so in most cases I would suggest the 6.8.