[W&B] What is it ? Cone lenses

[Milan Zahorcak]

Chris,
 
The lens on my deck is a Jamin-Darlot, full-plate combination with "cone
centralisateur" with the full-complement of portrait and landscape bits and
pieces.
 
There was some discussion (and much confusion) a while back about the proper
names for these things.  Turns out that in the 1850s, they started out as
just portrait lenses.  Then the 'cone' was added for unlikely optical
benefits, then it was offered with a landscape conversion option.
 
The term "cone centralisateur'' describes just the conical rear end and any
lens that has it, simply has a cone centralisateur rear end.  On the other
hand, there were also combination lenses with or without cones.  Another of
those noun, proper noun, adjectives issues.
 
Soooo . . . depending on configuration, certain Jamin/Jamin-Darlot/Darlot
portrait lenses could be had as:
 
1. a portrait lens
 
2. a portrait lens with cone centralisateur
 
3. a combination portrait/landscape lens without con centralisateur
 
4. a combination portrait/landscape lens with cone centralisateur
 
http://www.pacificrimcamera.com/milanpub/Misc-pics/variations2.jpg
 
More fun,
 
mz
 
 

-----Original Message-----
From: woodandbrass-bounces at kjsl.com [mailto:woodandbrass-bounces at kjsl.com]
On Behalf Of Christopher Wright
Sent: Friday, June 08, 2007 9:09 AM
To: Collectors of 19th Century Cameras &Photographica
Subject: Re: [W&B] What is it ? redux


Hello Steve:

Seems like there is a confusion as to which lens we are talking about.  I
was responding to Milan's picture of the large lens on a table outdoors, not
to your camera and lens question. 
Serves me for jumping into a discussion without first reading the miles of
emails beforehand.
Sorry for the confusion. 
(BTW: Your camera looks to me like a kind of "mouse trap" a la Talbot, for
making Calotype negatives.)

Christopher Wright




 .  At 5:31 PM -0400 6/7/07, SBShohet at aol.com wrote:

Hello Bernard and Christopher,

Bernard, I think your idea is the most reasonable so far.  There are indeed
interior threads inside the slightly extended lips at both ends of the lens
tube. (these look like filter threads on conventional lenses, though they
might be there to receive the 'collets' which hold the glasses in place).
There are certainly no Jamin or Darlot marks anywhere.

Christopher, I'm still a bit unclear of how a Centralizateur worked or was
arranged, but I can tell you that the optics here were not particularly fast
like a Petzvel. The glass diameter is about 30 mm. which with the stated
focal length of 175 mm. translates to a speed of just a bit better than F 6.


The mystery continues.  Steve


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