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View Full Version : Massive Gauss Type Lens to be identified !



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Q.G.
09-27-2010, 12:36 AM
Ask any LF photographer, and you'll be told that absence of a focussing mount doesn't mean the lens is meant for fix-focus use.
;)

(I'm not saying, by the way, that it is an LF lens. Just that a focussing helicoid is not the only way to focus a lens).

Holes in the lens could really only serve one purpose: cooling or heating.
Cooling would imply great heat, and that you only get in a projection system.
Heating would be used to prevent a lens fogging up, which would fit with it being meant for aerial use.

ausphoto
09-27-2010, 01:08 AM
Ask any LF photographer, and you'll be told that absence of a focussing mount doesn't mean the lens is meant for fix-focus use.
;).

Indeed, but that would ONE BIG MONSTER bellows system... :whistling:

Stephen Frizza
09-27-2010, 03:48 AM
Im curious I just saw this lens and i was thinking this may not be a projection lens but could this be a small 1940's ground to air war time search light lens? as in for spotting bombers at night?........ my imagination runs wild.

AgX
09-27-2010, 06:07 AM
Search lights would not need any complicated lens system. All search lights I know of use a huge (parabolical) mirror and a very small mirror to shield the lamp/burner to the front.

Stephen Frizza
09-27-2010, 07:33 AM
I have seen those kind of search lights but i have seen search lights with lens too. though none with a lens like the one shown here. my imagination ran wild because of the holes in the lens.

cowanw
09-27-2010, 03:01 PM
Could it be to let water in and out for an underwater lens?

AgX
09-27-2010, 03:09 PM
Water would reduce the refractory effect of any glass lens.

Dan Fromm
09-27-2010, 06:32 PM
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
09-27-2010, 08:04 PM
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.
09-28-2010, 04:11 AM
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
09-28-2010, 04:56 AM
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.
09-28-2010, 05:12 AM
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
09-28-2010, 07:46 AM
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
09-28-2010, 09:11 AM
ausphoto,

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

Q.G.
09-28-2010, 12:32 PM
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
09-28-2010, 04:19 PM
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
09-28-2010, 06:37 PM
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
09-29-2010, 01:24 AM
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
09-29-2010, 02:21 AM
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.
09-29-2010, 02:28 AM
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?