Any Jamin catalogs? from a case study of Jamin (Darlot) cone centralisateur

[Ron (Netherlands)]

I have yet to see a reasonable clear explanation of what the optical concept is behind the “Cone Centralisateur” and “Cylindrique” version.
.

Wasn't it the 'unique' sellingpoint of having in facto two lenses in one, i.e. one for portrait and one for landscape?

I have just updated Darlot only era catalog data to the pdf above.

Tnx, nice work. Btw it is Benjamin French & Co….

And - if of any interest - here is the thread with some info on the two Darlot achromats in my collection:
https://www.largeformatphotography.i...gs-at-the-edge

Fwiw: the lens with the Darlot inscription on the barrel has a lens diameter of 60,75 mm (focal length from what is written on the lens edge: 315 mm);
the lens without an inscription on the barrel has a lens diameter of 60,57 mm (focal length from what is written on the lens edge: 335 mm).

[mhayashi]

Good evening from Tokyo, everyone.
I have updated the pdf based on my sample measurements of Jamin cone centralisateur No.4 and No.5.
The file is suffixed by 20250721.pdf in the #9 reply.

https://www.largeformatphotography.i...=1#post1732690

It looks like the cone series are based on f5 design.
So I guessed the other FL of unmeasured models in the series based on f5 and the assumed lens opening diameters.

The focal length measurements are based on the regression methods available here.
I didn't use the infinity focus measurement and assumed the zero Y intersections,
where Y is the delta between two measurements of the object in different distance from the lens,
and X is the corresponding magnification difference.
I took at least 5 sampling measurements for regression.

The regression method is well described by this excellent page by Wagner Lungov.
https://apenasimagens.com/en/measure...-focal-length/

[landstrykere]

If you know any other catalogs of Jamin cone centralisateur, let me know!
I’m interested in the descriptions before 1867.

I am no lens collector but used to searches in digital French material about aspects of early photographic period.

if you still have not found, you could ask on https://www.collection-appareils.fr/phpBB3/index.php Couple people there very knowledgeable who may know about one of these catalogues. Slim chances though.

there is a library, biliothèque Forney, dedicated to catalogues of all kind of manufacturers and shops, for different countries/languages, with a core covering France 19th c. You could ask if they have Jamin material:
https://sabf.fr/selection/select10.php

a known shop selling antiques lists a 1856 Jamin cône in its museum/exhibition part:
https://www.antiq-photo.com/collecti...entralisateur/
you could ask them if they have brochures/catalogues

In France during Jamin worked on lenses,
the metric system “mesures usuelles” was used
https://en.m.wikipedia.org/wiki/Unit...ment_in_France

just a precision on units. This Wikipedia article and its sub-article may be fuzzy. They state clearly anyway the key point: "mesures usuelles" were for retail, in fact more generally usual ones in ordinary life (of common people). Metric system was the only one used in academic, scientific, technical publications from 1840 (decree of 1837, so a period to adapt).

The "pouce métrique" was not metric at all but called so because its reference standard, the "pied métrique" was redefined as a 1/3 of the meter, no longer the thousand years old dimension of the "pied du roi" (ie. Charlemagne) but 1/3 of a meter. Duodecimal system and 1/2, 1/3, 1/4, 1/8 fractional use was retained. Actual dimensions, of pied (royal) and "metric" pied, and therefore 1/12 of it, ie. pouce, were in acceptable difference range for commoners, popular duodecimal habit kept. It was an hybrid way to propagate decimal metric system. School was the key tool of propagation. But again this did not apply to technical, scientific, publications, that were using metric system.

main sources for digitalized documents are national library, Bibliothèque Nationale (BNF), site "Gallica", and specific for industry and technology, CNAM (Conservatoire National des Arts et Métiers).
This is for instance a 1860 catalogue of Derogy on CNAM:
https://cnum.cnam.fr/PDF/cnum_M9871.pdf
first two pages about lenses. Diameters in mm (then lines). But no focales, instead numbering as per intended plate size (sizes already fractions of a metric bit wider plate than the Niépce-Daguerre whole plate: 18x24cm) (yet inches dimensions are used for some other plates....). For instance in first table the regular lens for 18x24 (whole plate) is the one with 84mm diameter, no focal provided...

Jamin lens design was presented in Bulletin de la Société Française de Photographie , 1855 p. 341 (november) , and results of an examination by comity members was summarized in same publication in 1856 p. 170 (may), these publications were referenced in notes in the 1989 book of Rudolf Kingslake. But have been since, digitalized. Unsure by the way if Kingslake went to read this material or had someone get a copie at BNF, or just used the references already in Fabre 1889-1902 "Traité encyclopédique de photographie." These articles don't provide sketches, yet interesting to read:

https://gallica.bnf.fr/ark:/12148/bp...367b/f346.item
https://gallica.bnf.fr/ark:/12148/bp...244w/f173.item


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about the lasting of older units:
a catalogue of an exhibition of photographs in 1861. It lists the photographers and their exposed works, some with mention of the lens used, and focal in mm:
https://sfp.asso.fr/collection/image...P_0453bib_.pdf

page 21: "Objectif double demi-plaque de M. Jamin, 0m, 25 de distance locale; diaphragme 0m, 015"
page 29: "Portrait grandeur nature, obtenu directement avec objectif 8 pouces de M. Jamin."
page 34: " Portraits; grandes épreuves obtenues directement avec objectif de 6 pouces Jamin Darlot"

see how inches are still used: objectif de 6 pouces, de 8 pouces ... This is not a technical publication yet makes wonder if the dimension given for the lenses in inch are just habit translation of mm dimensions by Jamin shop, or if Jamin used both in its sales.
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[mhayashi]

landstrykere, thank you for your detailed guidance.
Very helpful.

Ihave looked into BNF in past but no lens detaied table of Jamin and Darlot were found so far.

Yes, I correspond with Sebastian of Antiq-photo once in a while for samples I want.

The bulltin you mentioned is probably the first obvious article about Jamin cone centralisateur.
I also read that too.

Pouce convention seemed to be used in lens design for a while even after metric system was introduced, as described somewhere this convention originated from telescope optical designs.

[landstrykere]

I correspond with Sebastian of Antiq-photo once in a while for samples I want.

The bulltin you mentioned is probably the first obvious article about Jamin cone centralisateur.
I also read that too.

if Sébastien Lemagnen has no earlier documents of maison Jamin, then there may be the option of bibliothèque Forney.
Yes the mention of the cône in 1855 in Bulletin de la Société Française de Photographie is certainly the oldest one, unless there are early notes of Jamin somewhere.

biographic data about him is btw, not clear, some mention he died in 1867, others "unknown", but this page of Ministère de la Culture mentions (as per Musée d'Orsay):
https://pop.culture.gouv.fr/notice/joconde/M0250000308
"Jean Théodore Jamin est né à Paris le 26 juin 1827 et décédé à Saint-Mandé le 25 février 1903. Opticien et photographe à Paris : rue Saint-Martin dans les années 1850, au 13 rue Chapon dans les années 1860 et 1870. Associé de Voland et Labourieu en 1861. "
another page on French government web, with one of his photograph or photograph by his atelier, mentions he received a prize at the international exposition of Nice in 1884:
https://imagesdefense.gouv.fr/fr/por...medaillon.html
this sourced as mentioned there, in a two volumes work published from compilation of notarial documents and published by Archives nationales:
https://francearchives.gouv.fr/fr/article/94367343

Pouce convention seemed to be used in lens design for a while even after metric system was introduced, as described somewhere this convention originated from telescope optical designs.

yes but these are British inches (2,54mm) not French pouces :-) . Somewhat similar to current film sizes, FOMA in Czechia ie. metric system, manufactures sheet film in british inches: 4x5, 5x7, 8x10.

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Uncommon to read similar topics in Anglosphere web, as typically Anglosphere people ignore what is not in English. Congratulations for the searches across languages and good continuation :-)