Upload & Sell: On
Yeah, I think I know what you mean. I cleaned a lens for a friend not too long ago (The Sigma AF 24mm f/2.8, Nikon mount) and there was a doublet with a lens on top and a loooong straight that was as you say "doing nothing" - just shifting a node. When I saw that I wondered why they didn't just make the lens more of a pancake - but then again maybe this element is different lengths in the different mounts to compensate for the different flange depths. <shrug>
Some on-line images of the lens being discussed.
Not a very sharp lens BTW... Rather mediocre all around...