Massive Gauss Type Lens to be identified !

[cowanw]

Could it be to let water in and out for an underwater lens?

 

[AgX]

Water would reduce the refractory effect of any glass lens.

 

[Dan Fromm]

Could it be to let water in and out for an underwater lens?

Um, one of the lens' barrel's jobs is to keep the dark in. The monstrosity's perforations fail miserably at that.

I have one dive camera. Eumig Nautica, to be exact. Its lens is well sealed. It also has a supplementary w/a lens that screws into the front. Not waterproof, but it doesn't have to be. I've known cavers who used Nikonos cameras; caving is much the same as diving, with a lot of banging around added. Nikonos have well-sealed lenses.

 

[ausphoto]

There are some underwater cameras that had flooded lenses, I recall, but all of that as small stuff and had problems with the different refractive indices of water or different salinity (as I recall). This thing is far too heavy and would have been far too unwieldy for underwater use anyhow..

 

[Q.G.]

I doubt that it would be an underwater lens. But can't underpin that believe with reasons.

The fact that the lens is large and heavy doesn't speak against it. People are doing more going underwater than scubadiving along a reef to take holiday snaps.
Allowing water into the lens would eliminate pressure problems, which would otherwise require a rather sturdy construction. However, unless you also flood the film or sensor, you will have to have a water barrier at some point. And no better place than at the front end of the optical system (i.e. the front lens), no worse point than somewhere between the lens and the film/sensor.

That water reduces the refractory index is a given you have to deal with anyway when submerging a camera, AgX. You have to design a lens with that in mind.
The differing refractive index at different depths and salinity would be a bigger problem in a fixed design lens.

A bare barrel like this one would appear not to be the whole deal. It is obviously meant to be mounted inside something else, to be pat of a bigger apparatus. And that something else will do a fine job keeping the dark inside. So i wouldn't worry about the wholes from that respect.

But i still think it is a projection lens.

 

[AgX]

That water reduces the refractory index is a given you have to deal with anyway when submerging a camera, AgX. You have to design a lens with that in mind.
The differing refractive index at different depths and salinity would be a bigger problem in a fixed design lens.

One characteristic of lens systems employing glass elements is the quite large difference in refraction between glass and air. Exchanging air for water within a lens will largely reduce that difference, and thus would not be beneficial even when taken into account. Exchanging glass by water is more interesting as you could drain a lens and save weight.

 

[Q.G.]

You're right, of course. But, and that was my point, not an unsurmountable problem.
Yet, i still don't believe it is an underwater lens either.

 

[Stephen Frizza]

well im just wondering......yes this is a lens but who says this lens is designed to produce an image? perhaps its just a lens designed to project light in a specific way? if you get what i mean

 

[AgX]

ausphoto,

How do you know that it's a US lens as stated by you on Flickr?

 

[Q.G.]

well im just wondering......yes this is a lens but who says this lens is designed to produce an image? perhaps its just a lens designed to project light in a specific way? if you get what i mean

I'd say the design is far too complex not to be an image forming lens.

 

[ausphoto]

ausphoto,

How do you know that it's a US lens as stated by you on Flickr?

Well, a bit of long bow may be, but it came from the US and (according to seller) came from a lot that had only other US aerial camera stuff with it

 

[ausphoto]

Ok, let's refocus this discussion ...

1) The lens is a near-symmetrical double Gauss lens with eight elements in six groups.

(http://www.flickr.com/photos/heritagefutures/5017011205/)​

2) The external menisci were set with the concave side pointing outward, but that may have been the result of storage (to avoid protruding lens surfaces being scratched accidentally)

3) The lens mount has large perforations either for cooling or heating of the lens assembly

(http://www.flickr.com/photos/heritagefutures/5017013119)​

4) The lens mount as found is in itself complete and has no (space for a) diaphragm.

5) The centre of the lens mount (on the smaller side) has an external thread, which suggests that a cover/cone could have been screwed on here. A narrow groove would provide a light tight end to this

(http://www.flickr.com/photos/heritagefutures/5017606862)​

This may suggest that the part that protruded from the unit was the section with the smaller diameter, rather than the section with the wider one. That interpretation is supported by the orientation of the fasting screws on the lens mount.​

6) There are no markings except for numbers on the metal fittings.

The number 1095-1821 is cast into the central lens mounting ring
http://www.flickr.com/photos/heritagefutures/5017004801​

The other numbers are scratched in and follow the same pattern: 1095-1830 to 1095-1840
http://www.flickr.com/photos/heritagefutures/5017003919​

The lens glass is unnumbered​

7) The reconstructed focal length of the unit is about 31-inches with an aperture of f6.3

8) The 'viable' interpretations are

a) an aerial camera lens
b) a lens from a projection system​

What's now needed is to first find a positive ID of the lens pattern:

http://www.flickr.com/photos/heritagefutures/5018936535/​

and then once that is clear, work out where the lens came from.

 

[AgX]

The lettertype `l´ in casting and writing indicates that it is not german. Otherwise it would be `1´.

The thread of the screw might be another indicator of origin.

 

[ausphoto]

AGX... the '1' has a little ascender in the casting (hard to see on the pic), so it could still be German....but I agree with your observation as to scratched in numbers.. Also, the '7' on one of the rings is a dead give-away... writing style is US or British....

I will look at the screw, but expect it to be Imperial dimensions (as are all the other measurements I made...)....


so, yes, lens is either US or British manufactured

 

[Q.G.]

AGX... the '1' has a little ascender in the casting (hard to see on the pic), so it could still be German....but I agree with your observation as to scratched in numbers.. Also, the '7' on one of the rings is a dead give-away... writing style is US or British....

You two are very brave men, daring to decide that on the strength of how numbers appear.
What and where is the evidence that in Germany all ones, or sevens, aren't written the way they appear on this lens?

 

[ausphoto]

Well, having once been a German, it was/is my experience that Germans DO write their sevens with a horizontal bar mid-way down the stem, and most Germans would have a little ascender on their '1' and not just a straight stroke "|"...
Certainly the '7' was the rule ten or so years ago (to distinguish it from the '1'...) and this thing is not a new lens...so, I'd take that as a reasonable assumption..

But the clincher for me is that the measurements are Imperial and not Metric...

 

[Q.G.]

An assumption that may appear reasonable. Yes. But appearances can, and will, be deceptive.
(Have a look at how sevens appear on Zeiss lenses, for instance.)



Anyhow: the imperial measurements offer more 'solid' evidence.
Could still be, of course, that a lens maker normally using metric units supplied optics to be mounted inside units made by someone using imperial units.

 

[ausphoto]

Managed to design a quick and dirty lens mount an stick the lens on a tripod. That allowed me to estimate the focal length a bit better. Looks like that the effective focal length of the lens is 24 inches. This means, given the diameter of the first element, it's more likely to be an f5.6. Doesn't look as powerful as the aerial lenses should be...but have put out various feelers beyond APUG

 

[michaelbsc]

Doesn't an aerial lens need to be wide field?

I don't really know much about aerial photography, but 24 inches onto a 10 piece of film doesn't seem very wide.

What am I missing?

 

[Marco B]

Doesn't an aerial lens need to be wide field?

I don't really know much about aerial photography, but 24 inches onto a 10 piece of film doesn't seem very wide.

What am I missing?

Entirely depends on the flying height. "Normal" aerial photography can be done at modest heights and may use smaller focal lengths, but I remember reading a recent article about US spy plains flying at heights up to above 10 km, and they used cameras with focal lengths inbetween 20-40 inches if I remember it well...

 

[Marco B]

One thing that bugs me about the "aerial" camera lens identification, is that the "mount" in the middle of the lens just contains 3 fragile bolts. Just imagine these being subject to the vibrations of air turbulence... Unless this lens was somehow securely "clamped" down in a structure we don't see, I can not imagine how it would hold.

And compare that with the many thread holes on this Fairchild aerial camera lens below (at least what they appear to be, I don't know much about these aerial cameras, maybe it is something different). I already see some 4 holes(?) for bolts this side of the lens, and I guess it is bolted down with 8 or 9?

But maybe someone else knows better how these lenses were fitted in the aerial cameras... :confused:

This is a lens made by Fairchild Space & Defense Systems:

From this page:
http://www.aerialphotolab.com/apl_museum.htm

And here is an F56 aerial camera with 40 inch lens:

From this page:
http://mysite.verizon.net/yenrav/20cms/cameras.htm

Managed to design a quick and dirty lens mount an stick the lens on a tripod. That allowed me to estimate the focal length a bit better. Looks like that the effective focal length of the lens is 24 inches. This means, given the diameter of the first element, it's more likely to be an f5.6. Doesn't look as powerful as the aerial lenses should be...but have put out various feelers beyond APUG

Last, according to this Camerapedia page, the K-17, K-18 and K-22 came in versions with 24 inch / F6 lens option. So your values seem anything but strange...

 

[ausphoto]

Thanks for the link to arialphotolab..!

See here for lens mounted in makeshift bracket:
http://www.flickr.com/photos/heritagefutures/5038518501/

 

[Marco B]

Here is what is apparently one of the camera systems used on the U-2 spy plane, with a rotating lens unit. The U-2 had a serious payload limit (see this Google Books link), so they had to adjust existing K38 cameras. Maybe that explains the "holes" in the lens? Simply safe weight wherever possible?

And three other images of a different camera system that was definitely on the U-2. Unfortunately, the pictures are not clear enough to fully understand the lens/shutter assembly and how it was fitted to the rest of the camera body:

From this page: http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=9169

 

[Marco B]

Thanks for the link to arialphotolab..!

See here for lens mounted in makeshift bracket:
http://www.flickr.com/photos/heritagefutures/5038518501/

Wow, that really makes you appreciate the size of the beast!

 

[greybeard]

An intriguing thread.

One possibility that seems not to have been mentioned is that the holes were added for a special purpose, unrelated to the original application. In the 1950s there was a lot of military interest in rocketry and missilery, and not much on the market in the way of specialized tracking cameras. (There are historical pictures of tracking cameras built on antiaircraft gun mounts and the like.) The holes may have been put in simply to allow the lens to more rapidly equilibrate in temperature when exposed to cold (high altitude, perhaps, or actic conditions), or to prevent damage during rapid depressurization. And maybe it is one-of-a-kind because the idea turned out not to have been very good!