[Leica] Re: RE: film tape glue flash

[Jim Brick <jim_brick@agilent.com>]

At 05:23 PM 5/31/01 -0400, Mary and Stan Kephart wrote:
>Friends,
>
>Warning!  I messed up a roll of 120 film big time by ripping off film from
>the reel.  Lots of fog, maybe because of the longer strip?
>
>MJK
>
>--Love is kind.


Mary,

Sorry to have to dispel your theory... I'll answer your LF questions soon... :)

For 40 years I have been ripping off 120 tape. I even pride myself in the
ability to produce a really big flash. But big is relative. The amount of
light, and its wavelength, will do nothing to your film except "perhaps"
directly under the tape itself. That is, the film that is stuck to the
tape. That's even debatable as there is a layer of glue still there.

When you pull the tape off of the film (or paper backing) the rest of the
roll is either curled up or loaded onto a reel, depending upon how you do
it. The point being, the film is not laid out flat with emulsion pointing
directly at the tape that you are about to rip off. And even if it were,
the amount of light generated is exceedingly minuscule. Film reciprocity
effects make it useless light. This light has no ability to penetrate
anything. Certainly not through layers of anti-halo and backing and
emulsion, and not even the silver halide molecules in the emulsion if it
were laying right there.

As I said, been ripping the stuff for years, even trying to out flash
yesterday's flash. Many years ago, Kodak 120 film tape was spectacular. But
the flash has no brilliance, is "cold" light (electroluminescence) and has
no ability to fog film.

I have "cold" light luminous tape all over my darkroom that is much much
brighter than the very short lived "cold" light flash. The reciprocity
characteristics of film dictate that a giant number of concurrent (or
consecutive) flashes would have to happen to be even barely detectable (if
at all) on most films. Easier on super sensitized astro film than ordinary
camera roll film.

Folks, this is not a problem. If you have a roll of fogged film, IT IS NOT
from the minuscule film/paper glue flash. If it were, don't you think that
this would have been an issue with Kodak over the past 40+ years. And Fuji,
Agfa, etc... 

But it isn't.

Every lab in the world rips off the tape, in the dark, many with previous
rolls hanging right there, emulsion out, a few inches away, waiting to go
into the dip & dunk processor. I used to be part owner of a lab. Done this
thousands of times. Lots of flashes. No fog.

Jim