Bob, you must realize I have reached the age where words sometimes
escape me. I remember them eventually but since I write pretty much
free-hand I must sometimes paraphrase, as in this case. Of course, the
effect I was describing is halation. In the days of glass plates it
could be very serious but self masking printing methods like printing
out paper can, to some degree, mitigate them by allowing what amounts to
burning in the highlights. It was common practice with glass plates to
coat the back with a sort of caramel. This was dark brown and helped
absorb some of the light reflected from the back of the plate. It soaked
off in processing. I remember their being instructions for coating the
unexposed plates in some very old books. Halation is still a problem
with flexible film but less so, partly because the index of refraction
is closer to that of air but mostly because its thinner.
Perhaps my use of the term "flare" was not a good choice because
the effect of halation in old photos is often blamed on lens flare. They
may sometimes look similar but are from very different causes. The
pictures of the insides of factories, for instance, where the area
around windows is blocked is mostly from halation rather than flare,
although flare can cause some of it.
On 3/17/2017 3:40 AM, bobkiss caribsurf.com wrote:
DEAR RICHARD,
FYI, the tech term for flare within film, especially that resulting from image making light passing out of the back of the film base is "halation". And the layer of gelatin with soluble dye on the back of the film was called the antihalation layer and dye. You can see in many old photos and movies large balls of fuzzy light around highlights or any light sources in the shot. That halation was pretty hellacious! LOL!!!
CHEERS!
BOB
------------------------------------------------------------------------
*From: *"`Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
*To: *"pure-silver@xxxxxxxxxxxxx" <pure-silver@xxxxxxxxxxxxx>
*Sent: *Friday, March 17, 2017 2:20:36 AM
*Subject: *[pure-silver] Re: Update On 1975 Kodak Film Pack
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] 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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Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL