[W&B] What is it ? Non d'Oh ! Vous, aussi ?

[Christopher Wright]

May I?

In the 40's when the search was on to make a faster lens than the 
ones available at the time (mostly landscape types; didn't Talbot and 
Daguerre both start off with telescope objectives?), Dr Petzval won 
the day with his arrangement.  There were, however, other contenders 
for the honor, and Th Jamin, #13, Rue Chapon, on the top floor of the 
Hotel Montbrisson, offered his customers (and to the Academy of 
Sciences) with what is essentially a Petzval arrangement, save that 
the rear portion is much larger than in Petzval's design.  When I use 
a Centralisateur, I notice a larger sharp zone, "sweet spot."
Jamin's identifying on the barrel the Landscape arrangement (front 
group in back, reversed) and the Portrait arrangement (complete set 
of glasses) is, I think, a clever way of promoting the lens, making 
it easier for the customer (not much changed there!) to remember 
which went where.
In addition to being a fast lens, like most Petzval-types, the 
Centralisateur can be made even sharper, expanding it's already large 
sweet spot, with the use of internal screw-in stops, set at the 
smaller end of the "Cone" section.
It's use would have seen Daguerreotypes and Collodion wet-plate.

Hope this helps...

Christopher




At 3:31 PM -0400 6/7/07, SBShohet at aol.com wrote:
>Cher Colleagues,
>
>OK, I'll bite: what's a Centralisateur?
>
>And as for you Milan, you can visit any time.  Good food, tolerable 
>beds and lovely cows,
>but they lack wooden bras.
>
>Amicalement, Steve
>
>
>**************************************
>See what's free at http://www.aol.com.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.kjsl.com/pipermail/woodandbrass/attachments/20070607/b652b082/attachment-0001.htm