Re: Unloading IR film Re: Halation

[Ken Sinclair <photo1@xxxxxxxxxxxxxxx>]

Barry,

The felt at the "mouth" of cassettes, while being generally visible (or
hominid) light- tight, do not stop the shortwave IR radiation to which the
film is sensitive. You will find a similar problem exists with some sheet
film holders which use a "felt" to stop hominid light entering the film
holder when the darkslide is removed.

You will notice that the "caps" on HIE film containers are not the familiar
grey colour that Kodak uses on nearly all other 35 mm film... the grey caps
are not IR radiation proof.

>Which raises the question:
>
>I can see why film with no anti-halation (hey,some of my best friends
>are halations!) layer needs to be loaded in the dark, but once you've
>re-wound the leader into the cartridge, why is it necessary toUN-load
>the camera in teh dark? Isn't the cartridge light tight? If not, why
>isn't  halation aproblem following the first frame of expoure?

I would hope that the body of your camera is able to "stop" IR radiation
(except when the shutter is open). Thus, once the film is on the sprockets
and the first frame exposed, the seal on camera body back will prevent all
light leaks. If your camera body were to leak "enough" IR you might find
that there is no "clear" film between frames once processing is finished.

It pays to take all possible precautions....

ken


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