I am very curious about this: what kind of developer are you
using? Some developers, noteably _fresh_ D-76 have no fog suppressor
in them and tend to produce a little fog. Once used the developer
acquires some bromide and some iodide from the film which tends to
suppress fog. Kodak discovered that freshly mixed D-76 would produce
very slightly higher speed if a small amount of bromide was added, about
0.25 gram per liter of stock solution.
Now, what I am curious about is whether fog suppressors have any
effect on the print through. Fog suppressors work because emulsion fog
(as opposed to being lightstruck) come from a different mechanism in the
halide crystals. So, its possible to reduce the inherent fog with
little loss of sensitivity to light. I have no idea what effect the ink
has on the emulsion but some experimenting might be interesting. I
don't suppose the ink is slightly radio active (?)
On 7/15/2015 3:09 AM, C.Breukel@xxxxxxx wrote:
Since I also sometimes experienced print through, and had the idea that it had
to do with pressure of the roll in the film back, I decided to repeat Tim's
experiment below. At first I did not see the imprint, but if you look very
carefully one can see the figures and forms imprinted in both the non-exposed
film straight out the wrapper and a roll of film ran through a Zenzabronica SQ
(also non exposed),
The print through is actually lighter than the B+F (which is relative high due
to the home brewn developer I use), so it seems that the black ink used for the
numbers is somehow slightly de-sensitising the film. So it's less responsive to
light, although the density difference is subtle, it can pop up in the final
print.
Then I decided to expose a third roll, deliberately over exposing 1/2-1 stop from my
normal speed (10 ASA) and I took a "busy" subject (an old riveted steel bridge
in the city centre), prints form this test did not show imprint. I do have to carefully
check a few more prints which are currently drying.
Best,
Cor
On 7/7/2015 7:33 PM, Tim Daneliuk wrote:
I developed a couple of rolls of APX 25 Ortho today - One, out of the
box, one, transported through a Hasselblad A12 with no exposure.
Both showed signs of print through. This seems to vindicate Richard
Knoppow's contention that this is an ink/backing paper issue, not a
roller transport or exposure-related problem. So, this would point to
a manufacturing defect that isn't a consequence of use, magazine
pressure, or other after-the-fact artifact.
Interesting.
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