Question about Lerebours et Secretan lens

[lungovw]

Hello, I bought this lens recently and I was wondering why such a landscape lens would have washer and Waterhouse stops at the same time. Is the position of a diaphragm something flexible? These two are quite apart. Could be the Waterhouse a later add-on? Does anybody have an explanation or guess about that? Have you seen this before? The serial number is 7456 and is engraved on lens' border as well. I did not evaluate carefully the focal length but it is about 300 mm. Lens diameter is 55 mm.

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[Steven Tribe]

The barrel looks a little long for a dedicated Lerebours landscape lens. Most of them at this time were either fixed barrel or pressure sleeve types.

My first idea is that this a Petzval barrel where the front achromat has been placed at the rear and the top plate with pill-box has been added from another lens. All parts look like Lerebours products.

The landscape lens would have not performed well with these washer stops so far from the achromat and the Waterhouse cutout and slot were quickly added. The section of the barrel in front of the WHS would function as an excellent lens hood!

The Waterhouse adaptments were definitely made later and a lot of brass was cut from the sleeve. I enclose a phot of one I have with a slightly later serial number, where the WHS is placed in a different position as respect to the focussing drive and engravings.

[goamules]

I was thinking the same thing as Steven: that this lens is an altered Petzval. I've seen a few strange lens contraptions over the years, usually made by someone that doesn't know what parts from a box go where.

[lungovw]

Thanks for the inputs. Now that you mentioned I also noticed that the tube is quite long indeed. But I went to check the actual distance between washer and lens and realized that the tube does not affect it that much. The lens is sort of recessed inside the tube and the pill-box enters the tube 13 mm taking the washer much closer to lens than what we may assess from the outside. It seems like the designer wanted a long tube while keeping a more regular proportion between the diaphragm and lens. The WHS is anyway much closer. I made a drawing that is not technical but gives a good approximation. That construction allows the lens to be moved back and forward 30 mm (more than other regular landscape lenses?) . But what for? maybe a special camera. What still seems really strange for me is about having such different positions for washer and WHS.

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Red is the WHS and green is washer.

[Steven Tribe]

As Alice would say "Curiouser and Curiouser"!

The countersunk pill box makes sense, but the deeply set lens doesn't - unless the ring at rear Stamped "28" is just a friction fit. Or is "28" part of a mount with a lens at the bottom?

I get a distinct feeling this is made up from a Lerebours petzval and other parts - perhaps from another maker. I have a number of lenses from different makers in Paris in the 1850's where parts are interchangeable.

[lungovw]

More info collected: I measured the focal length. It is aprox 255 mm. It does not cover whole plate but it works for 1/2 plate. In Lerebours 1853 catalogue it is mentioned a lens "pour vues" for 1/2 plate with 57 mm diameter (like mine). In Étienne Wallon's Traité elementaire de l'objectif photographique he says that for this type of landscape lens (having a biconvex rear lens and biconcave front lens) the distance from stop to lens is f/5. With 255 mm focal length this gives 51 mm. I measured from pill-box to lens surface and got 42 mm. I find this coherent as the lens thickness is not considered nor the exact washer position. I am also considering that glass and tube belong together due to the same number that shows up in both. The number 28, I think it was punched later, maybe an inventory number, it even noticeably jammed the rim, it wouldn't be a factory standard. The attached pictures show the focal length calculated based on 8 measurements of magnification and showing a good fit. The recessed lens mount and the serial number in lens. It might be an assembly from other makers, a modified Lerebours, as Steven suspects, of it may be a special purpose original lens, for a special camera... I don't know.

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[Steven Tribe]

The punched 28 is not something a maker would make, except on flat brass. It is so easy to disturb the roundness and, thus,, the the threads. Everything about the cell looks professional and the lens looks absolutely right for a 1/2 plate achromat. Even the distance from the lens in its current position to the stop position underneath the lens hood is standard.

The sunken position of the achromat within the barrel is in contradiction with what was considered good practice at the time. I think it will even restrict coverage.

It will remain an enigma, I think!

[lungovw]

Steven, I think so too. But anyway, it is registered here, let us see if a second sample or any other info ever shows up.

[Steven Tribe]

Could be solved at some stage.

New information does appear from time to time. We have just found out that JFS (J.F.Shew) sold Lerebours in London under his own name, but using a serial number sequence from Paris.
Pont et Princelle have yet to produce their monograph covering Lerebours, so real knowledge about the range of Lerebour's early products is not available at present.