john_van_v
Well-known
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.
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.
Roger Hicks
Veteran
(1) A narrow 'waist' allows a smaller and more efficient shutter as compared with behind-the-lens
(2) The compromises in lens design are different (cf Voigtländer Prominent)
(3) You can change front components with film in the camera.
Or maybe I'm misunderstanding your question. What alternative are you proposing?
Cheers,
R.
(2) The compromises in lens design are different (cf Voigtländer Prominent)
(3) You can change front components with film in the camera.
Or maybe I'm misunderstanding your question. What alternative are you proposing?
Cheers,
R.
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 Contaflexes 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 Contaflexes.
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.
Regards,
Brett
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john_van_v
Well-known
Wow, that has to be the most complete description on the Web, I am sure it will get RFF many hits.
My thinking yesterday and today is that:
- if old lenses are going to be applied to new digi cameras, there will have to be a back lens, and
- if photography is to survive, there will have to be manually/mechanically tripped shutter releases (such as the epson), possibly electronically timed.
So, all this together suggests that a back lens, with a narrow waist old-school shutter design in front (that would include aperture and simplify the digital electronics to on-off-memory store) would give the best of all worlds. (I would add a mechanical rangefinder in the mix somewhere, possibly on top of the shutter.)
Optics are obviously fairly sophisticated, so I cannot imagine how this compressor would work--but I would probably spell it Komperssor
(BTW, I just received a purely-pristine Kodak 135mm F4 Xenar(?) for only $15 that I CANNOT wait to test with film--Deckel-M39 adaptor?)
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Sumarongi
Registered Vaudevillain
Re *rangefinders* having behind-the-lens leaf shutters:
Voigtländer was able to make a 50mm/1.5 lens for their Prominent, *the* Nokton; and there's been also a very rare Japanese behind-the-lens leaf shutter-CRF with a 50mm/1.4, allegedly.
*edit*: Kowa Kallo 140, or just *Kallo 140*, or *Kowa 140*, see: https://www.rangefinderforum.com/forums/showthread.php?t=43884
phofseth
Established
The Prominent had a complete interchangeable lens, not a front-component only. But both that, the contaflex and the Retina had a central shutter.
It might be worth considering whether the difficulties of flash photos using otther shutter designs made a difference .
p.
It might be worth considering whether the difficulties of flash photos using otther shutter designs made a difference .
p.
Yes, but as ph mentions above the Prominent does not use modular lenses like, for example, some of the Zeiss Ikon rangefinders did. It's got a behind the lens shutter which Voigtlander seemed to prefer, given they also chose the configuration for their Bessamatic and Ultramatic SLRs. As far as the Nokton is concerned, I expect the absence of a reflex mirror in the Prominent, and consequent ability to place the lens closer to the film plane would have been a factor in Voigtlander's ability to achieve a f/1.5 lens.
Cheers,
Brett
Dwig
Well-known
The "why" is very very simple. They were done that way so that the shutter and its complex connections to the body (focusing, cocking, release, ...) could be permanently attached. It also had the advantage of avoiding the very large leaf shutters needed when the whole lens was mounting in front of the shutter so that it could interchange as a unit.
This approach had it optical challenges, the primary impact of which was the very limited range of alternate focal lengths.
BTW, this is "interchangeable front cell" design. "Convertible" lens designs are a totally different animal.
Sumarongi
Registered Vaudevillain
But then, a very recent thing, we have the *Neptune Convertible Art Lens System* by Lomography --
They even have an own youtube playlist for that thing:
https://www.youtube.com/playlist?list=PL2h3ozgMM9f4rDVODAHZL4lMCbd6l9RNO
Is that actually *Convertible*, or is it just -- although there's nowhere a shutter in the lens -- some sort of a reincarnation of the post-war Contaflex?
Dwig
Well-known
Classic "convertible" lenses, as opposed to interchangeable component lens sets that have been tagged as convertible in recent times, are lenses where the basic form uses the complete lens (all available pieces-parts). They could be "converted" by removing and/or rearranging the components.
Classic examples would be the Goertz Dagor and and the Schneider Symmar. The Dagors are true symmetrical designs, and you achieved the alternate FL by removing the front cell, which doubled the FL. The Symmar is a semi-symmetrical design where the front and rear cells have the same basic design but have different FLs. The complete lens yields the "advertised" FL and longer FLs are achieved by using one of the cell by itself, always in the rear position.
Using these lenses, and their competitors, as converted lenses fell out of favor. Most marketing materials for the Dagors in the last 80-90 years omits mention of converting. Schneider redesigned the Symmar to optimize its performance when complete at the expense of the performance when converted. These tweaked lenses, the Symmar-S, were no longer marketed as convertible.
oftheherd
Veteran
Were the results that bad, or just inconvenient? I have a couple or three convertible lenses, two for 4x5 and one for 8x10. I have yet to use any of them. They sit sorrowfully abandoned on a shelf. Two as I recall are Schneiders, and the 8x10 is a Turner-Reich.
I have no idea how well they worked, or didn't work, but Fujica had a Fujicarex camera that as I recall was interchangeable front cell in 35mm, 50mm and 80 or 85mm. It had a really strange shutter/mirror arrangement as I recall.
someonenameddavid
Well-known
Yashica Lynx IC f1.4 is not that rare
as discussed recently the 35mm skoparon is retrofocus and completely in front of the lens
BillBingham2
Registered User
I've got a set for the 4x5 View kit I got from my father. As I remember the results they were good. My gut tells be they were pretty good for the day but might not stand up to newer glass.
I'm hoping that the lens engineers in China will kick some older tires and see about coming up with some great glass. Seems they are learning about excess capacity and capitalism.
B2 (;->