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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