The Nikkor-T series uses ED glass, which reduces the secondary spectrum of chromatic abberation. Schneider's webpage (http://www.schneideroptics.com/photo...tele-xenar_hm/)
says that the Apo-Tele-Xenar HM lenses use "special optical glass" for a "clear reduction in the secondary spectrum", which is the same. One would expect some performance improvement over lenses not using ED glass -- whether it will make a noticable difference is another question.





There is a 400 mm f5.6 Apo-Tele-Xenar and 400 mm f5.6 Apo-Tele-Xenar Compact, but both are in Copal 3 shutters, and the first weighs 1270 g and the second 916 g. The 360 mm f8 Nikkor-T ED is in a Copal 1 and weighs 800 g (http://www.europe-nikon.com/specific...=523&catId=151). VERY heavy lens, very heavy lens, heavy lens.....