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Mistery lens: Carl Zeiss Jena Biometar 2,8/105 !
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PostPosted: Thu May 03, 2012 12:07 pm    Post subject: Mistery lens: Carl Zeiss Jena Biometar 2,8/105 ! Reply with quote
I have it. It is _not_ Biometar 80 nor Biometar 120 for medium format.
Google is unable to find anything about it. It does not appear in the 2009 Kadlubek catalog.
Do you know anything about this lens?


Description (I don't have the photos with me, but I will post them here later):
It's a lens apparently without the external shell. Somebody has made a custom optical unit externally combining this stripped? one and other lens.
There is no mount and no trace of a screw thread that could enable mounting it into some focusing assembly ending with the mount.
Its diameter is clearly less than of Biometar 120, so it doesn't look to be made for P6. It is about the diameter I would expect from a 35mm format FF longish 2.8 lens.
I've tried it freelensing style and it works, I can reach infinity as well with it 2..3 cm away from the camera mount.
Best is the aperture, it has the uncountable blades that give the round iris. It is placed between a front optical block and a rear optical block, so I would say the lens is complete but for some mounting/helicoid focusing mechanics.


Any clues? Ask your friends too Smile


PostPosted: Thu May 03, 2012 12:11 pm    Post subject: Reply with quote
Great find. Sounds like enlarger lens but let the experts tell.


PostPosted: Thu May 03, 2012 2:40 pm    Post subject: Reply with quote
Some infos in an Taiwan blog http://blog.xuite.net/fdchen/lenses/22423280 .


PostPosted: Fri May 04, 2012 9:42 am    Post subject: Reply with quote
calvin83 wrote:
Some infos in an Taiwan blog http://blog.xuite.net/fdchen/lenses/22423280 .


Mine looks very similar, just that it has the inscription a front ring and nothing is written on the cylindrical body at the rear end.


As far as Chrome can translate the chinese there, the blog author also doesn't know much about it, just that it is a prototype.
I have made a helicoid mount for it from the body of a Pentacon 50/1.8 clone (Autorevuenon) and tried it.
At F4 is better than at F2.8 (estimated with the lighmeter in the camera, as there are no inscriptions for aperture) in terms of sharpness.
The bokeh is nice I would say (here at F4):


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PostPosted: Fri May 04, 2012 10:02 am    Post subject: Reply with quote
Enlarger lens


PostPosted: Fri May 04, 2012 2:00 pm    Post subject: Reply with quote
Isn't it more likely a barrel mount lens for large format? Why would an EL be coated? Also, 2.8 is fast for an EL, the Schneider 105mm Componon-S I have is f5.


PostPosted: Fri May 04, 2012 2:10 pm    Post subject: Reply with quote
iangreenhalgh1 wrote:
Isn't it more likely a barrel mount lens for large format? Why would an EL be coated? Also, 2.8 is fast for an EL, the Schneider 105mm Componon-S I have is f5.


I am by no means an expert in enlarger lenses, but indeed from what I've researched lately only the cine (projection?) lenses seem to be that fast (or even faster).
To me the lens looks too thin to be a large format lens (since it's obviously much thinner than my medium format Biometars, both 80 and 120mm ones). Now that I've made a temporary adaptation of it I had to measure, the rear barrel is about 42mm in diameter - but plain, without any thread.


PostPosted: Sat May 05, 2012 10:40 pm    Post subject: Reply with quote
Most enlarger lenses are coated and some are fast so that's not a 100% cogent argument that it's not one.
Often especially bigger labs use fast lenses - when you have to make 500 or more prints per day some extra stops will be very usefull.

I think that it's not a projection lens as Carl Zeiss Jenar Projector lenses had very different dimensions and usually different names than their photo-taking counterparts (even with the same optics inside). But Zeiss Jena made also very large projectors for auditoriums (and lenses for them) - which might be another shoe, as it's very hard to find informations about them (they are rare because they were only made for Universities, "Palace of the Republic" or other larger public institutions of the GDR)

It might be also a photo-taking lens but I can't find any details to prove that.

Could you take a pic of the rear-side?


PostPosted: Sun May 06, 2012 1:24 am    Post subject: Reply with quote
Projector lenses don't have apertures, or at least, I've never seen one with an aperture.


PostPosted: Tue May 08, 2012 5:50 pm    Post subject: Reply with quote
ForenSeil wrote:
Most enlarger lenses are coated and some are fast so that's not a 100% cogent argument that it's not one.
Often especially bigger labs use fast lenses - when you have to make 500 or more prints per day some extra stops will be very usefull.

I think that it's not a projection lens as Carl Zeiss Jenar Projector lenses had very different dimensions and usually different names than their photo-taking counterparts (even with the same optics inside). But Zeiss Jena made also very large projectors for auditoriums (and lenses for them) - which might be another shoe, as it's very hard to find informations about them (they are rare because they were only made for Universities, "Palace of the Republic" or other larger public institutions of the GDR)

It might be also a photo-taking lens but I can't find any details to prove that.

Could you take a pic of the rear-side?


Sure, here it is. The crenellated ring can be rotated and controls the aperture.


It took me some time to do it, as I had non-destructively arranged it for use, complete with focusing and shade (true franken lens with parts from others):


The filter diameter seems to be 46 mm (I don't know to include the screw depth). As said, the diameter of the tube on the back side is 42mm. I have counted also the blades, there are 15.
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