"Canon's new 400mm f/2.8L III and 600mm f/4L III lenses are a lot lighter and much better balanced than the II series." Those words were easy to type, and it's all too easy to dismiss as "so what?", but what kind of work went on behind the scenes to make that statement a reality?
It might be the fact that Canon's III series telephoto prime lenses look a lot like... well, lenses. But what you may not realize is that they were rebuilt from the ground up and completely left the II series behind in many aspects. You probably have been made aware that one of the biggest changes with these lenses, and the reason such a reduction of weight occurred, is from moving many of the big glass elements back towards the mount side and in turn could be made smaller and lighter. But really think of what it must take to engineer all that and maintain world-class sharpness, contrast, autofocus speeds, and everything else high-end L-series glass exhibits. It's mind-blowing.
Luckily for us, Canon got their top engineers together for an interview (PDF file) on what exactly went on behind the scenes to go from the II series telephotos to the III series.. Honestly, it's a lot to read and take in, and yes, there's a bit of patting themselves on the back that requires skimming by, but I felt it was well worth it in the end.
I've never met any of Canon's engineers, but I've spent a good deal of time around Sony engineers and I can say that these guys are truly unsung heroes of photography. The public doesn't know their names or titles, but they are thinking about how to advance photography day and night. And not only think it, but then go into work and do it. I love these guys.
Definitely check out this interview because it's an interesting look inside how product development works for the biggest name in photography.