 Posted: Mon Dec 12, 2022 2:12 am Post subject: |
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Posted: Mon Dec 12, 2022 2:12 am Post subject: |
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stevemark wrote:
I may be interesting to know that Minolta - before releasing the MD 2/85mm VariSoft - had a few more prototypes for their upcoming soft focus lens.
1) the most simple was a Triplet with an additional negative lens behind the triplet for varying the softness
2) another was a Tessar type with an additional negative lens either in front of or behind the triplet for varying the softness
3) there was also a Triplet with two negative lenses (one in front, one behind), both moving independently
4) then there was a Heliar type with an addional negative lens at the end; here we had three groups moving (a. front dublet plus negative center lens of the Heliar; b. rear dublet of the Heliar, c. additional negative lens at the rear)
5) the version which was chosen for production is a Tessar type as well, with an additional positive and negative lens at the rear. Three groups are being moved: a. the Tessar (fron) group, b. the positive lens behind the Tessar, and c. the negative lens at the rear (see here for the lens section: http://www.artaphot.ch/minolta-sr/objektive/163-minolta-85mm-f28-varisoft).
Focusing is done by moving the Tessar front group.
Varying the degree of softness is done by varying the distance between the last (negative) lens and the other five lenses in front. By doing this, not only the spherical aberrations are (=softness) are changed, but also the focal length.
Thus, to keep the focusing invariable while varying the softness, the front focusing Tessar group must have a slight additional movement. All this results in a pretty complicated mechanical construction - and in an equally high price, of course.
Just some background information ... I hope it is useful to some ...
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