Archived posting to the Leica Users Group, 2012/07/10

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Subject: [Leica] Daguerreotype Plate Sizes at 72 dpi
From: philippe.amard at sfr.fr (philippe.amard at sfr.fr)
Date: Tue, 10 Jul 2012 23:24:54 +0200 (CEST)

De : "Mark Rabiner " <mark at rabinergroup.com>
A : "Leica Users Group" <lug at leica-users.org>
Copie ? : 
Sujet : Re: [Leica] Daguerreotype Plate Sizes at 72 dpi


 Daguerreotype Plate Sizes were based on the avaible size of plate glass used
in windows. Well the full size would have been I don't know about the
cutting down into the quarter and sixteenth plate sizes the logic which was
used. You often see the list on the internet listed as inches. I've not yet
seen them metric. I think inches was a UK thing from way back was it not
also a French thing?


France went metric at the Revolution, circa 1789
the values of inches, feet, etc varied from one part of the country to 
another - it was decided to use a common system, 1790 - then the metric 
system was adopted in 1795.
At the time the Daguerotype was patented by the French Academy of Sciences I 
doubt that the window panes had standardized sizes, rather, the guys cut the 
glass to fit into the gap the joiners had made, by hand ...



http://en.wikipedia.org/wiki/Daguerreotype

Ok from this source here
Whole Plate:    6.5 x 8.5 inches    (16.5 x 21.5 cm)
Half Plate:    4.25 x 5.5 inches   (11 x 14 cm)


Really surprising maths 
WP = 354,75 cm2
HP = 154cm2
can't be half
the remainder is lost in translation :-)


I'm no scientist, I have doubts all the same here.


Now about the pixels, I'm sure that the English language version of PS 
allows for cms - after all don't Canada and Australia use them on a regular 
basis?


KISS principle ;-)


Amiti?s
Philippe




Quarter Plate:    3.25 x 4.25 inches    (8 x 11 cm)
Sixth Plate:    2.75 x 3.25 inches    (7 x 8 cm)
Ninth Plate:    2 x 2.5 inches    (5 x 6 cm)
Sixteenth Plate:    1.375 x 1.625 inches    (3.5 x 4 cm)
It appears  from this list the inche sizes were based on the original CM
sizes not the other way around.
Perhaps I should redo it with a straight to pixel from CM conversion.
Though I don't know what the math is on that.
Here is the source
http://cwfp.biz/platesizes.php




- - from my iRabs.
Mark Rabiner
http://gallery.leica-users.org/v/lugalrabs/


> From: Philippe Amard 

> Reply-To: Leica Users Group 
> Date: Tue, 10 Jul 2012 22:52:22 +0200 (CEST)
> To: Leica Users Group 
> Subject: Re: [Leica] Daguerreotype Plate Sizes at 72 dpi
> 
> Are you sure the unit used then was the inch?


I'm sure the photos will be
> better if you use cms


;-)


Nice idea about the format, unsure about the
> pixel count though.


AMiti?s
Philippe


Tous vos emails en 1 clic avec
> l'application SFR Mail sur iPhone et Android - En savoir
> plus.


========================================

Message du : 10/07/2012
> 22:04
De : "Mark Rabiner " 
A : "Leica Users Group"
> 
Copie ? : 
Sujet : [Leica] Daguerreotype Plate Sizes at
> 72 dpi


 Whole plate        6-1/2" x 8-1/2"     468 x 612 pixels
Half plate
> 4-1/4" x 5-1/2"     306 x 396
Quarter plate     3-1/4" x 4-1/4"     234 x
> 306
Sixth plate         2-3/4" x 3-1/4"     198 x 234
Ninth plate        2" x
> 2-1/2"         144 x 180
Sixteenth plate     1-3/8" x 1-5/8"     99 x 117

I
> worked the math on these plates sizes into pixels.

I plan on working up some
> images at these sizes which perhaps will have some
resonance in our photo
> DNA.

Sometimes I  plan on just entering the inch sizes at whatever resolution
> I'm
using on the print. As they are a bit small for the screen even.
I really
> don't know. Maybe I'll find myself using these all the time. Or
hardly ever.
> But It was fun doing it.


- - from my iRabs.
Mark
> Rabiner
http://gallery.leica-users.org/v/lugalrabs/



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Replies: Reply from mark at rabinergroup.com (Mark Rabiner) ([Leica] Daguerreotype Plate Sizes at 72 dpi)
In reply to: Message from philippe.amard at sfr.fr (philippe.amard at sfr.fr) ([Leica] Daguerreotype Plate Sizes at 72 dpi)