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Re: [Rollei] 5 element Xenar



So they did make this lens with front cell focusing. Interesting they would
forego this in the Welta Perle and use a helicoid focusing. Seems more
expensive than front cell focusing and I wonder if the results are really
that noticeable.

Speaking of convertible lenses there were the convertible Symmar lenses
that were not great with just the one cell. You had to stop down quite a
bit before edge distortion disappeared. But as the name implies, they were
somewhat symmetrical.


todd

Richard Knoppow wrote:
> 
> At 06:42 PM 02/08/2002 +0100, you wrote:
> >That's interesting indeed! Remember to report your results with this lens!
> >According to Schneider, this lens was also available with front cell
> >focusing, but I guess your version is better!
> >
> >I've read that the Unofokal lens can be used with the two rear elements to
> >get a tele effect. I will do some experiments with that. I guess I will have
> >to extend the bellows more.
> >
> >/Patric
> >
>   A single element of most symmetrical or semi-symmetrical lenses can be
> used alone, but the image quality will not be very good. Dialyte types,
> like the Unofokal, Goerz Dogmar, Goerz Apochromatic Artar, Kodak 203mm,
> f/7.7 Ektar or Anastigmat, etc., have no correction for coma. Neither does
> the Dagor or Dagor derivatives like the Schneider Angulon (sold originally
> as a tripple convertible!). Such lenses will perform at very small stops
> vis: f/45. The Zeiss Convertible Protar (Series VII or VIIA) has individual
> elements which are corrected for coma and perform much better as
> convertibles although not any better as combined lenses.
> ----
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk  

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End of Rollei Users list digest V10 #159
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