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12-04-2014, 05:25 PM   #1
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Pentacon six and Zeiss lenses

I just bought a Pentacon Six TL 6x6 Medium format camera with a Biometar 80 f2.8. It's a beautifully designed camera - I think in Art Nouveau or Art Deco style with nicely rounded lines and decorations. It has some flaws, yes I know them but one of the things that's so great about this camera is not the camera itself but the lenses.

It uses Zeiss lenses in Pentacon Six Mount like Flektogon 50mm, Biometar 80mm, Sonnar 180mm etc.

I have a question here:
- I was recently looking for a 70-90mm lens for portraits in addition to some good M42 135mm and 200mm Pentacons I have. Good Pentax lenses(fa77, a*85, etc.) in that range are very expensive for me - somewhere around 700-800$. Obviously, the Zeiss Biometar 80 can be mounted on Pentax digital bodies and I can use it aswell on my Pentacon Six. This seems like a very good deal to me. And I don't think anyone would object to the IQ of the lens. The question is then, why the heck is it so unexpensive, given that it's in the 70-90mm range, known to be very expensive? Why would anyone still want to get a (say) Pentax A* 85mm instead of the Biometar + adapter given that the latter is 4x less the price and possibly better in quality?

(Please don't get me wrong, I don't want to dump fa77 or a*85 here or any other lens. They seem amazing from the samples.)

12-04-2014, 06:41 PM   #2
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QuoteOriginally posted by misomosi Quote
Why would anyone still want to get a (say) Pentax A* 85mm instead of the Biometar + adapter given that the latter is 4x less the price and possibly better in quality?
Why are the 70-85mm Pentax K-mount lenses so much more expensive? The same is true regarding the CZJ Pancolar 80/1.8 in M42 of the same vintage as your Pentacon Six lenses. The Pancolar usually sells for well over $700 USD. Similarly, if Pentax medium format lenses are so great, why aren't they popular as adapted lenses for small format cameras? The answer might be in your assumption that the Pentacon Six lenses are of superior optical quality and will offer performance on APS-C equivalent to what they deliver for medium format.

I think it is a valid generality that quality medium format lenses perform impressively well for the large image circle that they must satisfy, but that the absolute resolution of those lenses is not particularly high.* The design challenges for a retrofocus 6x6 lens are similar to that of 35mm FF except that the image circle is almost twice as large and it is in servicing that space that compromise is made. I think you will find the adapted 6x6 format CZJ lenses to be adequate on the smaller format, but not stellar.


Steve

* The same is true for large format view camera lenses. High quality 35mm SLR lenses generally deliver higher resolution to the film than those made for the 4x5" format.

Last edited by stevebrot; 12-04-2014 at 06:50 PM.
12-04-2014, 06:57 PM   #3
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I have the Biometar 80/2.8 and Sonnar 180/2.8 in Pentacon 6 mount with K mount adapters (both zebra versions). The zebras are single coated lenses. There are also MC versions. They are sharp and those who know more than I do will be able to comment on the "Zeiss signature" of the images. Frank Glencairn used zebra versions of the Biometar 80 and 120 to film "Indiana Jones and the Spear of Destiny"; see https://frankglencairn.wordpress.com/vintage-zeiss-glass-on-modern-cameras/ . I don't see the point in comparing the Zeiss glass with the better Pentax lenses. It is a matter of what character you are looking for in your images. But the old Zeiss lenses are (mostly) great value and do a fantastic job. I have a Pentax FA 135/2.8 which is a great lens. But my Zeiss Sonnar 135/3.5 is a delight to use and gives fantastic results. I would hate to have to chose between them.


By the way, the zebras look fantastic on the K-01 - sort of Bauhaus design meets Marc Newson.
12-05-2014, 02:40 AM   #4
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Interesting thoughts, thank you.

Steve, I am curious about what you said of adapting larger format lenses to smaller format film/sensor. I don't know much about this, that's why I started the thread, but my assumption is that since on smaller film/sensor only a center portion of the lens is used, and since the center portion usually yields the best results in any lens, then the quality should be the same or somewhat even better than on the medium/large format film. I say "even better" because you may get rid of some bad corner sharpness for example. But again, this is just an assumption so correct me if I'm wrong.

PJ1, that's really an awesome find! And this is the very reason I picked those Pentacon M42 lenses I was mentioning - the samples on the Internet had character. They flare and they don't autofocus etc. but they got character and bokeh! Now there is also the practical reason, at least for me - having a lens that I can use on two systems means less money, less weight, less fuss. About the zebra look, it is indeed fantastic, I really like it and it fits so well with my white K-50.

12-05-2014, 03:46 AM   #5
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Generally speaking (and there are always exceptions) it is easier to design a sharp lens to cover a smaller area than a larger one. A medium format lens still needs to be sharp over most of the frame so the designer may sacrifice absolute sharpness in the centre to get acceptable sharpness near the edges. So comparing three 135mm lenses designed for 35mm, 6x6 and 4x5 respectively and looking just at a 24x36mm section from the centre the 35mm lens will probably be sharper than the 6x6 lens which will probably be sharper than the 4x5 lens. However when you come to enlarge from the entire negative the order will probably be reversed, since if you sacrifice 20% (say) in sharpness but double the size of your negative then you are still well ahead in overall sharpness once you have enlarged and printed.

So generally speaking a well designed 35mm lens will be sharper than a well designed MF lens if you are only comparing the centre area of the image. So be wary of thinking that a lens that is very sharp on MF will also be very sharp on 35mm or worse, APSC.
12-05-2014, 01:23 PM   #6
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QuoteOriginally posted by misomosi Quote
Steve, I am curious about what you said of adapting larger format lenses to smaller format film/sensor.
QuoteOriginally posted by Paul Ewins Quote
Generally speaking (and there are always exceptions) it is easier to design a sharp lens to cover a smaller area than a larger one. A medium format lens still needs to be sharp over most of the frame so the designer may sacrifice absolute sharpness in the centre to get acceptable sharpness near the edges. So comparing three 135mm lenses designed for 35mm, 6x6 and 4x5 respectively and looking just at a 24x36mm section from the centre the 35mm lens will probably be sharper than the 6x6 lens which will probably be sharper than the 4x5 lens.
What he said. It is painful, but true.


Steve
12-05-2014, 02:01 PM   #7
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QuoteOriginally posted by Paul Ewins Quote
So generally speaking a well designed 35mm lens will be sharper than a well designed MF lens if you are only comparing the centre area of the image. So be wary of thinking that a lens that is very sharp on MF will also be very sharp on 35mm or worse, APSC.
While this is generally true, as you say it's not a rule. The Pentax 645 FA 75mm lens is sharp enough in the center to use on the Pentax Q with excelent results. I haven't tried the CZJ Biometar 80mm like that, but I have used it on a Canon 5D where it's excelent. It's probably very nice on APS-C too. It is however two stops slower than most of the really expensive small format lenses in that segment.
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