[rollei_list] Re: changing lens formulas
- From: "Eric Goldstein" <egoldste@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Sun, 4 Nov 2007 20:21:23 -0500
The proof of automation enhancing precision can be found in factory
tolerance specs. One example is FL tolerance, which in the 50's was
about +/-5% and is now typically +/-1%. It used to be near impossible
for me to find a pair of prime lenses close enough in FL to make a
stereo rig; now it is trivial, even with some zooms...
Eric Goldstein
--
On 11/4/07, Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
> I have heard many references to automated production of
> lenses but I am not sure what this could include. The
> process of making a lens begins with a blank. In the old
> days this was a chunk of glass the right size broken out of
> a "pot" of glass but a later method was to mold the glass
> into the approximate size and shape for the element. The
> elements were then ground on machines which ground many
> lenses at once. Several steps are used to grind the lens
> from rough grinding to finished lens. About the only hand
> work I know of was the making of aspherical surfaces which
> is done now by automated machines. AFAIK such operations as
> centering and cementing must still be largely hand work
> although the determination of the center can be done by a
> sensor working an automatic centering machine. Centering is
> very important especially for elements wich are to be
> cemented.
> Lens mountings must be quite precise but are the sort of
> machining that can be done by CNC machines.
> To some degree the exact curvature and thickness of an
> element can be varied to compensate for small variations in
> glass constants. Usually, the glass is measured before its
> use in production to verify its constants. While glass
> manufacture has advanced a great deal there are still some
> small variations. These can affect all optical aberrations.
> I simply don't see that automated manufacure and
> assembly results in more precise production although it
> probably lowers cost. The fact is that some very fine lenses
> were made before automation.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
>
> ---
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