Originally Posted by john_van_v
I am trying to figure out if there is a benefit to this arrangement as we find on the Kodak Retina IIc, IIIc, IIC, IIIC, and some SLRs such as Contaflex
. It seems counter intuitive, since the rear fixed lens dictates how the front lenses have to be, and requires that the front lenses be floating.
Floating front lenses, from the evolution of the twin lens reflex, seem to be something you would want to get away from.
Maybe there is something I am not getting. Another reason I am curious, is that there is a need for fixed body lenses for diminishing digital formats -- pretty soon the tiniest sensors may be as good as the large ones.
I'm not quite sure what you mean by "floating" in this context. Perhaps you're suggesting front cell or front group focus rather than unit focus?
I own quite a few Contaflice and profess to be a fan of these well made and under-rated cameras. It should be noted that the earliest models such as the I & II featured a 45mm standard Tessar f/2.8 lens which was front cell focus.
Later models beginning with the III, followed by the IV, Super, Rapid, New Super, Super B, Super BC and S types, were greatly modified and featured unit focussing (meaning of course, the shutter housing moved with the lens).
My limited understanding of the disadvantages of front cell focus are that a compromise is required between near and far distance optical correction, and that optimising one trades off the other. Having said this, I have never read any very negative comments about the image quality of any Tessar lens fitted to any Contaflex model (including the I & II), all are generally considered to be of at least very good quality, the best recomputed ones are regarded as outstanding. As I have recently acquired a very late serial number Contaflex S with a rare recomputed Tessar, I plan to investigate this for myself further in the not-too-distant future.
Maybe you're referring more to the fact that interchangeable lenses of any focal length must all share the rear element permanently fitted to the camera body? This is true in the case of the Contaflex, it should be noted though, that other types of leaf shutter SLRs such as the later Kodak Retina Reflex models, and all types of Voigtlaender Bessamatic (amongst other makes) featured fully interchangeable lenses fitted with dedicated element groups. And of course in medium format, from 1957, the Hasselblad 500C and its derivatives used a unitary lens design (amongst others).
It's true that with the Contaflex installation, the need to share a common rear element places constraints on focal lengths and on lens speed (which to some extent is a result of having a leaf shutter SLR, in any case). I'm unfamiliar with the rangefinder installations, but the fastest lenses produced for the SLRs, that I am aware of, are the 50mm f/2 Septon for the Bessamatic, and a 50mm f/1.9 Xenon for the Retina Reflex.
It's fairly early days for me, but so far the results I'm seeing from the 35mm and 115mm Pro Tessar lenses I've acquired are surprisingly good for designs with inherent optical compromises and FWIW, the members of the Zeiss Historica Society rate them fairly highly. The biggest problem with them, of course, is that they are inevitably compared to those lenses produced for the Contarex...
It's also worth noting that it doesn't really matter if all the lens groups are in front of the shutter, or if some are behind it, with regard to changing lenses. In every case, the presence of the auxiliary shutter ahead of the film plane ensures that lenses may be changed without fogging film - it is an essential feature of the SLR configuration, even for the earlier fixed lens Contaflice.
As to the why part of your question - well, I suppose I'm speculating, but the Contaflex was
the first of its type. The mechanism is quite complex, but reliable enough if maintained. (Later unit focus models are more complicated again). Having been inside a number of them to service them this year (mostly successfully), I speak from experience.
Perhaps, given the difficulties involved in developing a new type of SLR with such an intricate mechanism, Zeiss Ikon's engineers felt that front cell focus and a behind the shutter rear lens group was an acceptable design compromise. And it should be remembered that in the early 1950's, usage of an SLR with a wide range of interchangeable lenses, was nowhere near as widespread amongst the well-heeled non-professional users to which the Contaflex was pitched, as it is today. It was therefore probably not considered to be the major limitation it might be now be regarded as.