In article , jplater@netcom.com says...
>
>Thumbing through McBrooms Bluebook, he mentions that it is important to
>check the aperture leaves for signs of oil leakage. McBroom says that
>this can result when lubricant leaks when lenses are stored >horizontally.
>Well this is a new one to me. Does anyone have any opinions about this
>statement?

Hmmm... It is hard to figure what causes it. I treat my lenses well
and they are never heated (another cause of oil on the diaphram leaves
that I have heard of) and are always carried and stored face down,
yet two of my Nikkors (I have had many, so this is not common with
Nikkors, except for the 55mm f2.8), a 55mm f2.8 and a 135mm f2.8,
acquired oil on the diaphram leaves. So, I dunno.
Hope This Helps