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Thread: Lerebours Serial Number - Rice Writing

  1. #111

    Re: Lerebours Serial Number - Rice Writing

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    Hi, I just got a Lerebours & Secretan lens, the serial number is 7492. I got it on a 2nd hand website in France, but I didn't managed to get any informations about this lens. It has the rice number serial number (see next post)
    Last edited by tymeorama; 7-May-2019 at 11:15.

  2. #112

    Re: Lerebours Serial Number - Rice Writing

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    What was unexpected for me is that the rice writing-serial number is seen twice on the back lenses (inside and outside)

  3. #113

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    Re: Lerebours Serial Number - Rice Writing

    Yes, I have seen another with a lens with both surfaces marked.
    I have added this lens to the sn/data list.

    Perhaps this is a good opportunity to mention that our good friend Grubb of Dublin engraved the edges of his aplanatic lens in the same way - or at least, some of them. Text was "Grubb Patent XXXX".

    If you don't have access to an early catalogue, measure the focal length and/Or the glass diameter and someone will give more information!
    Attached Thumbnails Attached Thumbnails image.jpeg  
    Last edited by Steven Tribe; 8-May-2019 at 04:58.

  4. #114

    Re: Lerebours Serial Number - Rice Writing

    Quote Originally Posted by Steven Tribe View Post
    If you don't have access to an early catalogue, measure the focal length and/Or the glass diameter and someone will give more information!
    Here are the dimensions of my lens:
    Mount thread: M68x0.5 mm
    Lens hood thread: M61x0.5 mm
    Front lens diameter: approx. 52.5 mm
    Back lens diameter: approx. 55 mm
    Total length: approx.102.3mm

  5. #115

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    Re: Lerebours Serial Number - Rice Writing

    This is a 1/4 plate (CdeV) Petzval of 12cm focal length and will cover 9x12cm. Made around 1854. This could be a "back" focal length (measured from the rear of the looong petzval!) rather than the real focal length.
    The lens dimensions for the smaller sizes are pretty constant for all french makers.
    1/6 plate 44mm
    1/4 plate 54mm
    1/2 plate 61mm

  6. #116

    Re: Lerebours Serial Number - Rice Writing

    Thanks Steven! I have basically no knowledge in large format photography :do you have any link that explain the 1/4 plate thing? I started to look at the articles I've found in this forum, but I hadn't find yet an easy explanation of this.

  7. #117

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    Re: Lerebours Serial Number - Rice Writing


  8. #118

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    Re: Lerebours Serial Number - Rice Writing

    Something new of some interest, perhaps.
    We have a problem with Lerebours et Secretan's missing serial numbers (both the scratched lenses sold in other's brass, as well as a quite long sequence of missing serial numbers). I have made the suggestion that they may have lost their brass machining facility for a period. But perhaps they lost their supplier of brass tubing?

    This could be an explanation of the strange lens below. That L & S sacrificed completed brass Petzvals to make, perhaps 2 landscape lenses. Normally, I would have said that the modification is not original - that the lens had lost its rear pair and the original barrel had been cut down, fitted with the front fixture to look like a typical French landscape lens.

    But the "conversion" looks very professional. So perhaps L & S still had a brass working workshop, but were cut off from obtaining new tubing?

    Later:
    This is, of course, a sleeve - rather than an original barrel, which has been fitted up with internal threads to take an (oversize) lens cell and an end cap.
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    Last edited by Steven Tribe; 21-May-2019 at 00:13.

  9. #119

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    Re: Lerebours Serial Number - Rice Writing

    Hi Steven,

    Good catch ... talk about cannibalizing.

    Agreed that this looks like it's coming out of the factory. Or someone broke the Petzval and conversion to landscape was all that was covered under warranty ... ... just fun to think about it !

    Cheers,

  10. #120

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    Re: Lerebours Serial Number - Rice Writing

    Quote Originally Posted by tymeorama View Post
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    What was unexpected for me is that the rice writing-serial number is seen twice on the back lenses (inside and outside)
    I can't remember if I ever commented on this, since discovering the tiny serial numbers. But Steven did. Maybe their purpose is to aid keeping the two rear lenses together for assembly. I believe the refractive index varies slightly even with the same type of glass, crown and flint. So when the lens grinder makes the curves he has to optimize each surface for that particular lens pair. Depending on how these were finished (put in brass mounts), they may have wanted to make sure the pairs remained together.

    So that begs a question: if a Lerebours has the scratched serial on one lens, is it always on the other? My number 5038 does. I'll have to pull out my other to see.

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