[rollei_list] Re: Identifying 2.8F models...the 3.5/75 six elements (again)
- From: "Peter K." <peterk727@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Mon, 2 Jan 2006 16:32:46 -0800
Yes Richard. As a group meeting the citeria I would say that makes sense. .
On 1/2/06, Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
>
>
> ----- Original Message -----
> From: "Peter K." <peterk727@xxxxxxxxx>
> To: <rollei_list@xxxxxxxxxxxxx>
> Sent: Monday, January 02, 2006 3:02 PM
> Subject: [rollei_list] Re: Identifying 2.8F models...the
> 3.5/75 six elements (again)
>
>
> OK Carlos, I have the Rollei 75 Years book, also written by
> Prochnow. On
> pages 140 and 141 it stated the following with regard to the
> model F:
>
> "Of course there were other improvements that had their
> share in the great
> success of the "F" models. One of these was the new,
> six-element Planar 75mm
> F3.5 lens which was introduced rather quietly with the third
> version of the
> 3.5F. Shortly after, Schneider followed with a 75mm Xenotar
> F3.5, likewise
> made up of six elements. The new optical formulas served to
> meet the
> performance data guaranteed to Rollei, which were difficult
> to attain with
> only five element. Production costs remained unchanged. The
> 80mm F2.8 Planar
> and Xenotar lenses did not have these problems and thus
> retained their five
> elements."
>
> So here is a book endorsed by Rollei and written by Prochnow
> where he claims
> the 6-element version were done to improve the performance
> of the 3.5 models
> and the interesting note is that it is clearly stated that
> PRODUCTION COSTS
> REMAINED UNCHANGED.
>
> This is why I stated this.
>
> Peter K
>
> However... This can also be interpreted as meaning
> that the production cost of the five element lens was too
> high because it was difficult to meet the minimum standard
> of performance with it. The additional element and
> additional cemented surface _should_ have resulted in a more
> expensive lens _unless_ the rejection rate was sufficiently
> lower to make up the difference.
> In fact, its rather puzzling. Certainly the five
> element designs deliver very good performance. For some
> reason, the conventional six element Planar design, so
> widely used in small format cameras, was rejected for the
> f/2.8 lens, where it should have made even more difference.
> Perhaps it has something to do with mechanical factors,
> maybe depth or weight, which might have been less
> significant with the slower lens.
> Unless there are business records from the time still
> in existence knowing the complete story is probably
> impossible.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
>
>
> ---
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--
Peter K
Ó¿Õ¬
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