[pure-silver] Re: Speed rating of glass plates

Hello Richard,
Thanks for responding. I have a several old "British Journal Almanac" so that would be a good start. In several of the unopend plate boxes, there were sheets of paper with formulas for film developpment, times. I'll have to have a closer look. Still, I wonder if any of the glass plates had the modern equivalent of at least 50 iso. I've some group portraits where you can see that somebody moved their head, or hand.... two ghost images, so exposure times must have been quite long. No wonder they had those chairs with the neck brace to keep the head steady as the person dozed of during exposure :) No wonder all these portraits are so stiff looking.
They make beautiful contact prints. And a 5x7 plate was a perfect size; good proportions. 8x10 seems a bit off for portrait work, especially with the long side of the back in the vertical position. And not as heavy. 

Thanks,

Bogdan


Richard Knoppow wrote:
----- Original Message ----- From: "Bogdan Karasek" <bkarasek@xxxxxxxxxxxx> 
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Friday, May 29, 2009 6:06 PM
Subject: [pure-silver] Speed rating of glass plates



hello,
Hope everybody is out burning film or sniffing hypo in the darkroom . :)
I have a number of exposed 5x7 glass plates, they are portraits, family, children, couple, single, done in a studio. From what I can make out, i.e people sitting in cars... probably 1920's?????
Does anybody know what would have been the ISO of these plates? I also have boxes of 4x5 and postcard size SEED's glass plates that are marked, "High Speed" which would be what speed? 

Any historians out there???

Cheers,
Bogdan
Any markings on the other plates? I have a little stuff on very old plates and will look. About the only way to get an idea of speed in modern terms is to look at the recommended exposure chargs and use the "sunny 16" rule. While there were several speed rating methods beginning with Huerter and Driffield none was very reliable and manufacturers often exagerated the speed. The exposure charts _must_ be reasonably accurate. A good source of information on at least British stuff are old eiditions of the _British Journal Almanac_ The advertising is often the most interesting part and some manufacturers included short form catalogues with film data, etc. 

--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there. 




--
________________________________________________________________
 Bogdan Karasek
 Montréal, Québec                     bogdan(at)bogdanphoto.com
 Canada                               www.bogdanphoto.com

                    "I bear witness"
________________________________________________________________ 


=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your 
account (the same e-mail address and password you set-up when you subscribed,) 
and unsubscribe from there.

Other related posts: