Re: [Rollei] Zeiss S-Planar 120, errata/addenda

[bigler@ens2m.fr]

  From Roberto:
> > ...please explain me what the "S-Planar" means....

  From E.B.:
> ...this kind of lens is at their top image quality at ratios 1:1
> (object = 6x6cm) -> 5:1 (object : 30x30cm) and not infinity-focus...

Some errata there, since we are in the Temple of Precision engineering
;-);-)

 -1- I used the improper notation for magnification. I should have
     written instead "1:5 (object : 30x30cm)". So 1:5 actually means
     what it means in elementary computation, i.e. 
     1:5 = 1 divided by 5 = 1/5 = magnification of 0.2.

     In order to remember this and as a mandatory homework during the
     Christmas break, by respect to Oberkochen Masters, I'll copy 50
     times what is engraved on the hassy 120 S-planar barrel : 
     "0.9 metres = Maßstab 1:5.5", 
     and as a mnemonic I'll sing something like : "Ich will den
     Maßstab gern..." (those of you familiar with Bach's cantatas will
     recognise what I mean, although this is not actually Easter times
     ;-);-)

- -2- According to Rick Nordin's "Hassy Bible" the 120 S-planar (same as
    the SL66's but in Hasselblad mount) is not actually at his best at
    1:1 (like purely symmetrical large format repro lenses, e.g. claron,
    ronar, etc...) but between 1:2 and 1:10. However it will of course
    perform better at 1:1 than a standard, infinity-focus optimised
    planar 80.

- -3- some additional info extracted from the original Rollei SL66
    brochure (1975). The maximum extension of the SL66 built-in
    bellows is 50mm. So in a sense the 120 S-planar is *the* ideal
    companion for a SL66. An extension of 50mm with a 120 lens means a
    limit magnification of 1:2.4. So without any additional tube or
    bellows you can directly work in the range of magnification where
    the 120 S-planar is at his top performance. The brochure mentions
    that you can focus down to 35cm, in fact this cannot be anything
    else but the distance between the object and the front part of the
    lens, not the total distance between the object plane and film,
    which at 1:2.4 magnification should be something like
    (2.4+1)*(120+50)= 58cm. I cannot imagine that the S-planar is such
    a telephoto desingn with a negative distance of (58-35)=23 cm
    between its nodal planes.

I hope that his will satisfy the most demanding RUGgers... 

Merry Christmas again to all and best regards from France,
- -- 
Emmanuel BIGLER         
<bigler  

------------------------------