[pure-silver] Re: High B+F with DS-10
- From: "Koch, Gerald" <gkoch02@xxxxxxxxxx>
- To: "'pure-silver@xxxxxxxxxxxxx'" <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 4 Feb 2005 11:57:55 -0500
Both Eastman 5231 and 5222 B&W MP negative films are on acetate stock. The base
has a slight magenta cast. They work very well for still photography.
The color in the film base whether it is acetate or polyester cannot be removed.
MACO produces a film with a colorless base. Fomapan R (a reversal film) should
also be on a colorless base.
Jerry
-----Original Message-----
From: John Black [mailto:jblack@xxxxxxxxx]
Sent: Friday, February 04, 2005 11:43 AM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: High B+F with DS-10
> >
> Most 35mm negative black and white film has a pigment in the
> support to prevent the conduction of light laterally through the
> material. The density is around 0.2. This pigment is permanent and is
> not affected by processing chemicals. It has no effect on the film
> other than to increase printing exposure a little. Back coated
> anti-halation layers do not affect conducted light. 35mm
> films are used in a way where the end of the film may be
> exposed to strong light. Without the pigment or other
> precaution the light will be piped along the support in
> enough quantity to fog some of the film.
Do you know if any modern (or presently produced) films are based on cellulose
truacetate instead of ployester? Kodak's 35mm films vary substantially in the
amount and character of dye contained. I read somewhere that cellulose
triacetate base that Kodak used was rater strongly gray colored (Tri-X?). My
results with TMY show less color to the base, which I presume is Estar
(polyester?).
Also, can the neutral density dye found in 35mm base be removed or lightened by
the bleach (dichromate/sulfuric acid) step in reversal processing? The newer
reversal processes seem to be able to make a clear based movie film out of even
Tri-X. Maybe they transfer to another film.
> In general fixing and washing have no effect on the fog level. One
> _can_ have turbidity of the emulsion caused by insufficient fixing and
> another kind of fog called dichroic fog can be caused by exhausted
> fixing baths. Dichroic fog is a thin deposit of very finely devided
> metallic silver on the surface of the film. It is called dichroic fog
> because it looks yellow by reflected light and cyan by transmitted
> light. It can also have a rainbow effect.
I think dichroic fog is the only kind I have not encountered yet.
> Fog level in film is partly inherent in the emulsion, partly due to
> changes due to aging, and partly to to the effects of excessive heat
> on stored film.
> Manufacturers put substanced into the film to stabilize the
> emulsion so that it doesn't continue to ripen or otherwise develop fog
> with age, and also anti-fog agents.
> Inherent fog varies with speed being generally higher as the film
> speed increases. Of course fog can also be produced by exposure to
> radiation of various sorts or being just plain light struck.
When using P3200 or Delta 3200 in 35mm, I cannot get below about 0.32 in NID
when energetic enough development level is used to aproximate rated speed.
Anti-fogants I have tried seem to lower the already poor shadow density of this
film. Should I just get used to this fog level with these two?
JB
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