[rollei_list] Re: Planar, Xenotar, Summicron

  • From: FRANK DERNIE <frank.dernie@xxxxxxxxxxxxxx>
  • To: rollei_list@xxxxxxxxxxxxx
  • Date: Fri, 27 May 2005 16:42:27 +0100 (BST)

According to the Canon Lens Work books, which are
interesting and inexpensive, they point out that Canon
uses 4 types of aspherical elements. The largest have
to be ground, then there are hot moulded using metal
masters (I believe Leica use ceramic masters to mould
their aspherics), replicated which I believe is a thin
plastic aspheric layer moulded onto a spherical glass
element and plastic moulded.
Some are for quality, some for miniturisation. I don't
have the books to hand so may not be quoting
perfectly.
Frank

--- Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
> 
> ----- Original Message ----- 
> From: "Jerry Lehrer" <jerryleh@xxxxxxxxxxx>
> To: <rollei_list@xxxxxxxxxxxxx>
> Sent: Thursday, May 26, 2005 2:01 PM
> Subject: [rollei_list] Re: Planar, Xenotar,
> Summicron
> 
> 
> > Peter,
> >
> > No, no!  I referred to INTERNAL elements which are
> never 
> > owner
> > cleaned. The Leica rumors had this as a 90mm f1.4 
> > lightweight lens.
> >
> > Jerry
> >
> > "Peter K." wrote:
> >
> >> Companies like Tokina made molded plastic
> elements for 
> >> some zoom
> >> lenses. Not sure of the compsite of plastic
> material for 
> >> a lens
> >> element, but they worked well. Of course they
> were 
> >> created via molding
> >> and far less expensive. The only problem with
> them was to 
> >> avoid
> >> leaving them in the sum or heat for any long time
> period 
> >> and also to
> >> avoide cleaning them alcohol.
> >>
> >> Peter K
> 
>    Kingslake discusses plastic lenses to a limited
> extent. 
> Kodak used them in some cameras. Also, its possible
> to make 
> an aspheric surface by cementing a plastic asphere
> to a 
> glass lens. The problem with plastics is that the
> range of 
> index of refraction and dispersion is limited.
> 
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx 
> 
> ---
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