Fast film has more fog even when new and gets foggier with age than
slow film. When the specs say base plus fog the base is the density of
the support and any anti-light piping or residual anti-flare. This
usually does not change with age. Anti-light piping is a pigment in the
support itself and is found mostly in 35mm negative still film. I am not
sure it is used on motion picture stock. It is not found on reversal
films and I don't think its used for color negative films. The
anti-flare coating is usually a dye in the back coating. Back coating is
a layer of gelatin on the back of the film to reduce curling. The dye is
usually removed by the sulfite in both the developer and the fixing
bath. Color films and some B&W films have a layer of dye under the
emulsion, between it and the support, which also prevents reflection
from the base to reduce or eliminate flare. This is also usually removed
or decolorized during processing. One problem with the decomposition of
"safety base" films is that the reaction products of the degradation of
the support can cause the dyes used for anti-flare to become colored
again, often in blotchy patterns.
Another cause of extra density is residual sensitizing dye. This is
found mostly in tabular grain films like T-Max and results in a slight
pinkish overall stain. The dye can be bound up in a way similar to
thiosulfate and fixer reaction products. While Kodak has stated that its
a sign of insufficient fixing it can remain even after extended fixing
with ammonium thiosulfate fixer and the use of two bath fixers. Sulfite
wash aids will get rid of it very quickly.
If the fog or base density is uniform it can be compensated for by
somewhat longer printing exposures but has no other effect. It does not
change the H&D curve of the film, at least if not too severe. The use
of an anti-fogging agent, like potassium bromide, can reduce fog,
especially on old film, but also changes the film curve, essentially
moving the exposure up the toe toward the straight line portion and
reducing film speed.
Remember that the ISO standard for B&W negative still film gives
about the minimum exposure possible with good shadow detail. The
standard requires some ageing of the film so that its relevant to film
when it reaches the market. The method used to determine speed of
reversal films, both B&W and color, for color films of all types, and
for motion picture films of all types is not the same and states
something closer to the optimum speed rather than the maximum.
Something like this can be found for B&W negative still film by
increasing exposure by about one stop over the box speed. This can be
beneficial for tone rendition and does no harm otherwise other than
resulting in somewhat denser negatives. However, it should not affect
over all contrast index although the increase in toe contrast may result
in a somewhat contrastier appearance of the same scenes.
The major film manufacturers put a good deal of research into
making the emulsions stable with time. For one thing film is a
perishable so the longer the shelf life the lower the cost of keeping
supplies fresh.
On 3/16/2017 9:02 PM, Richard Lahrson wrote:
Hi,
I just developed two rolls of outdated Ilford 3200 and
a quick read on the densitomer says 0.6 for filmbase
plus fog, so that's thick, but I exposed at 800 and
over developed some. I can print through the fog.
Faster films seem to have more filmbase.
Rich
On Thu, Mar 16, 2017 at 7:10 PM, Mike Kirwan <mkirwan@xxxxxxxxxxx <mailto:mkirwan@xxxxxxxxxxx>> wrote:
150 Do-it-yourself Black and White Popular Photographic Formulas
Purchased it in the early 1980’s along with a chemical balance
from a local Photo store that was changing hands…
Mike
*From:*pure-silver-bounce@xxxxxxxxxxxxx
<mailto:pure-silver-bounce@xxxxxxxxxxxxx>
[mailto:pure-silver-bounce@xxxxxxxxxxxxx
<mailto:pure-silver-bounce@xxxxxxxxxxxxx>] *On Behalf Of *kgriffit
*Sent:* Thursday, March 16, 2017 6:59 PM
*To:* pure-silver@xxxxxxxxxxxxx <mailto:pure-silver@xxxxxxxxxxxxx>
*Subject:* [pure-silver] Re: Update On 1975 Kodak Film Pack
Which Dignans book do you have?
Sent from my U.S. Cellular® Smartphone
-------- Original message --------
From: Mike Kirwan <mkirwan@xxxxxxxxxxx <mailto:mkirwan@xxxxxxxxxxx>>
Date: 03/08/2017 19:05 (GMT-08:00)
To: pure-silver@xxxxxxxxxxxxx <mailto:pure-silver@xxxxxxxxxxxxx>
Subject: [pure-silver] Re: Update On 1975 Kodak Film Pack
I am always amazed how well really old film can turn out. I
developed a couple of rolls of Efke R14 that I had purchased in
the 1980's. I shot at 40 ASA and developed in Modified Divided D76
(Dignan's book) for 4 minutes in baths A & B and wow, wow, no
fog, crisp images full of detail. I have about 20 rolls left, so
I think it time to put them to good use before I expire.
Now to try a few sheets 4x5 GAF SUPERPAN which expired in 1981.
Actually it states Military Expiration Date January 1981. The box
states an ASA of 250 determined by ANSI PH2.5. Probably will start
at 200 ASA with the same times. The modified D76 calls for a
small amount of bromide which probably helps with keeping fog to a
low level.
Once I have tested the GAF, will try a few sheets of Kodak Super
Pamchro-Press, Type B that expired in August 1954 - ha! almost as
old as me. Kodak suggests developing in DK60a, D-19 or DK-50,
and states the film is a fast Type B panchro of moderately fine
grain suitable for portraiture and other commercial work. My old
Kodak handbook suggests an ASA of 250 and develop between 6-8
minutes in the recommended developers. Not holding out any hope
for this film
Mike
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
<mailto:pure-silver-bounce@xxxxxxxxxxxxx>
[mailto:pure-silver-bounce@xxxxxxxxxxxxx
<mailto:pure-silver-bounce@xxxxxxxxxxxxx>] On Behalf Of Tim Daneliuk
Sent: Wednesday, March 08, 2017 5:24 PM
To: Pure-Silver Mailing List
Subject: [pure-silver] Update On 1975 Kodak Film Pack
Recall that I scored a new old stock Kodak Tri-X 2 1/4 x 3 1/4
film pack a couple of months ago. Expiry was Nov. 1975
Tonight I took a few shots with in in my Baby Speed Graphic and
103mm Ektar and then "robbed" them from the pack.
I normally expose TXP (when I had it) at ASA 160 and develop for 7
min in DK-50 1:1 (I happened to have that mixed up and
ready to go). In this case, in deference to the film's age,
I shot at ASA 125 and developed for 8 min.
I almost fell over - there is no visible fogging. The unexposed
edges - to the eye at least - look like normal Tri-X. Contrast
could be higher (a bit more development time) and exposure could
be just a tad deeper. Still, 40+ year old film that produces
perfectly normal negs is just a little bit shocking.
I think the remainder of the pack is likely to get exposed at ASA
100 and developed for 10 min.
Happy to answer any further questions...
P.S. DK-50 has the reputation of reduced film fogging. It sure
seemed to
work here.
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