"Hybrid" or polycarbonate lenses and aging

Paul Furman wrote:
Paul Furman wrote:

J. Clarke wrote:

On Wed, 06 Dec 2006 05:38:35 +0000, Paul Furman wrote:

J. Clarke wrote:

On Wed, 06 Dec 2006 01:16:35 +0000, Tony Polson wrote:

Now in the 1990s please state which Nikkor used glass aspheric
elements
and what the price was and the basis on which you assert that it used
glass aspherics and not molded aspherics.


We were just discussing the 20-35/2.8 glass aspheric versus the
plastic 17-35.


And what leads you to believe that it had a glass aspheric rather than a
molded one?


Hmm, I can't confirm that but I found mention of a comparable Tokina:
http://www.fredmiranda.com/reviews/showproduct.php?product=234&sort=7&cat=40&page=1

"Two Pioneering all-glass aspherical lens elements, one front and rear"


Hmm, not ground though but molded:

"Hoya Corporation, the world’s largest optical glass manufacturer, has
created a micron-tuned precision molding technique with the accuracy to
form aspherical surfaces to the thousandths of a millimeter."


And Sigma use nothing except moulded glass aspherics. Tamron use hybrid
glass-plastic. Minolta use(d) both and also used pure plastic aspherics,
notably in their series of Riva zoom compact cameras which managed to
have a 3X zoom constructed of only four elements, using two aspherical
elements.

David

"J. Clarke" wrote:

Now in the 1990s please state which Nikkor used glass aspheric elements


You could easily find this information for yourself. The reason you
haven't is that it shows your ridiculous assertions to be completely
without foundation.

Nikon lenses manufactured in the 1990s with precision ground aspheric
elements included the 58mm f/1.2 NOCT-Nikkor (deleted 1997), the
20-35mm f/2.8 AF(-D) Nikkor, which has already been discussed, and the
28mm f/1.4 AF-D Nikkor. All have at least one aspheric surface that
is machine ground.

None of these were cheap lenses, but they were not remotely as
expensive as you would like people here to believe.

In article ,
"J. Clarke" wrote:

then the whole lot of
us are damned fools for not plonking a RichA thread when we first saw it.

I think just plonking RichA should be enough. He's not going to change
and if the information is real, someone else will post it, too.

Lionel wrote:
[]
Only an issue if the front element is the plastic one, as glass
filters out UV. Haze filters also filter out UV.
Besides which, very few of us in this newsgroup would be using lenses
with plastic elements in the first place - they're generally found in
extremely cheap consumer cameras, not in DSLR lenses.

I believe I use plastic element lenses rather a lot - my glasses are made
from them! Comfortably light, seem to be reliable, don't scratch easily
in normal use, and I don't see any noticeable evidence of colouring after
a few years use. Oh, and more expensive than glass, IIRC.

David