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  1. #31
    AgX
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    Quote Originally Posted by Q.G. View Post
    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.
    Last edited by AgX; 09-28-2010 at 06:46 AM. Click to view previous post history.

  2. #32

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    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.

  3. #33
    Stephen Frizza's Avatar
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    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
    "Its my profession to hijack time" ~ Stephen Frizza.

  4. #34
    AgX
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    ausphoto,

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

  5. #35

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    Quote Originally Posted by Stephen Frizza View Post
    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.

  6. #36
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    Quote Originally Posted by AgX View Post
    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
    Last edited by ausphoto; 09-28-2010 at 07:42 PM. Click to view previous post history.

  7. #37
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    Ok, let's refocus this discussion ...

    1) The lens is a near-symmetrical double Gauss lens with eight elements in six groups.
    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
    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
    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:
    and then once that is clear, work out where the lens came from.
    Last edited by ausphoto; 09-28-2010 at 08:22 PM. Click to view previous post history.

  8. #38
    AgX
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    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.

  9. #39
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    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

  10. #40

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    Quote Originally Posted by ausphoto View Post
    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?

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