[pure-silver] Re: OA Kodak Safelight filters

Hi again,

Thanks for the clarification.  It all makes a bit more sense now.

Bogdan

Claudio Bonavolta wrote:


If you look at the curves (blue is density=absorption, i.e. light is retained 
by the filter), the OC cutoff starts at a longer wavelength than the OA and 
thus is safer with most VC papers.

Some VC papers (Bergger comes in mind) have a sensitivity curve that overlap 
the white part of an OC filter and will be fogged.
These papers require a red safelight, which cutoff must be at a longer 
wavelength than OC, 1A is around 600-620nm.

If you compare 1 to 1A, both red, you can see the former has a cutoff at a 
slightly longer wavelength (which may be safer) but also that it has a higher 
density in its transmission range that the 1A, so the darkroom will be darker 
and probably less comfortable (red is less comfortable than amber anyway).

I'm not that used to Kodak filter numbering in the red area but I suppose the 
1A will just be fine with most ortho material and will let pass more 
(inactinic) light and thus a bit more agreeable.
I suggest you check your paper manufacturer recommendations, and maybe do a test of the inactinic light, before opening a box ... 
Claudio Bonavolta
http://www.bonavolta.ch

----- Message d'origine -----
De: Bogdan Karasek <bkarasek@xxxxxxxxxxxx>
Date: Thu, 28 Aug 2008 11:36:14 -0400
Sujet: [pure-silver] Re: OA Kodak Safelight filters
À: pure-silver@xxxxxxxxxxxxx


Hi Claudio,

Thanks for the reference to the site.
Am I missing something but I fail to see a difference between OA and OC; I do contact prints with OC filters. on my safe lights. From the info, an OA filter would be just as good, or is there a nuance that I am missing???? Could I just as well be printing under an OA filter? 

OA

        

Greenish yellow

        

Black-and-white contact and duplicating materials, projection films

OC

        

Light amber

        

Contact and enlarging papers


Cheers,
Bogdan

Claudio Bonavolta wrote:


Description of the Kodak codes:
http://www.kodak.com/global/en/professional/support/techPubs/ti0845/ti0845.jhtml

For ortho material that requires a red safelight both OA and OC will fog your 
paper.

Claudio Bonavolta
http://www.bonavolta.ch

----- Message d'origine -----
De: Bogdan Karasek <bkarasek@xxxxxxxxxxxx>
Date: Thu, 28 Aug 2008 10:59:54 -0400
Sujet: [pure-silver] OA Kodak Safelight filters
À: pure-silver@xxxxxxxxxxxxx




Hello,
Can someone tell me under what circumstances one would use Kodak OA safelight filters?
I have seen instructions for printing paper that indicate use of a red safe light..... would that be a OC or OA filter???? 

I do strictly B+W and all my safe light filters are OC.

Cheers,
Bogdan

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

                  "I bear witness"
________________________________________________________________ 

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

                   "I bear witness"
________________________________________________________________ 

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

                    "I bear witness"
________________________________________________________________ 

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