Hi, Cotty wrote: > > On 17/10/03, [EMAIL PROTECTED] disgorged: > > >> It is between certain groups of elements and the action of focussing can > >> suck in / blow out miniscule amounts of dust in the air that must be able > >> to move in and out of the lens, otherwise it would not work. Any lens > >> acts like a small, slow pump - especially zooms. > >> > >> Which brings an interesting possibility - creating a vacuum > >inside............ > > > >Or you could do like Leica and others do with their binoculars. With an > >IF lens, seal it and fill it with dry Nitrogen so that there is no dust, > >no oxidation of greases and no internal condensation. > > > >Then charge about twice what the opposition does..... > > Wow. Fascinating! I never knew that. I suppose with an internal focus > lens, if there is compression of air (or nitrogen or whatever), then the > design must surely allow it to move to another chamber within the lens?
Hmmmm. Note I said IF, which is what the binoculars are. No change of volume, really. The parts just waffle about in the gas. If you want IZ (internal zoom) I think it is going to be much harder to design and manufacture. Or, in Leica's case, more expensive, sir. Ching! Thank you 8-))) m
