In article <4ab32v$aqr@newsstand.cit.cornell.edu>, d_ruether@hotmail.com says... (most deleted)
>(The short Nikkor teles, for instance, while great lenses for
>normal use, are very poor on tubes [they work better with achromats],
>while the 300mm f4.5 EDIF is both useful and excellent on tubes.)

I over-generalized with that statement. It should have been: The short
Nikkor MF teles of similar optical design (85mm f2, 105mm f2.5, 135mm
f2.8, 180mm f2.8), and the Nikkor 135mm f2, while excellent for
normal use, are very poor on tubes (they work better with achromats),
while the 300mm f4.5 EDIF (and some other Nikkor teles) is both
useful and excellent on tubes.
Hope this helps.