Richard Knoppow wrote:

Fascinating, antideluvian film. I am not sure of the
date anti-halation coatings were applied to roll film but
they certainly date back to glass plates. In fact threre are
instructions for making your own coating for plates in many
ancient phtography books.

Early plate "backing" had to be washed off. Many people
continued to buy unbacked plates for quite a while after
backing came out. Unbacked plates were fourpence cheaper
for a dozen 4x5 plates in 1915, but I think not having to
wash off the backing was the real reason unbacked plates
remained popular.

Kodak NC film was claimed to be "non-halation" on the packaging
either from its inception (around 1904) or very soon afterwards,
but I think that may have been a reference to the properties
of the thin support rather than an actual antihalation layer.
Verichrome (c. 1932) definitely did have an anti-halation layer;
Kodak showed pictures of a neon sign at night which made the
difference obvious.

Halation was much worse for plates
than film but its amazing that anyone would make film now
without the coating.

I looked at some Lucky SHD-100 negatives to see if I could see
signs of halation. The only thing that was obvious when examining
the negatives with a loupe was that the area aound the sky showed
a bit of grey spreading outside the frame. This sometimes seems to
happen a bit even with decent films, but the Lucky film is probably
worse in this respect. None of the pictures on the roll included
light sources other than sky. I did see the tiny scratches in the
sky that I had complained about earlier - this might be a batch related
problem, but I still found it annoying.

I think that some special purpose films such as Eastman 5302 and
5360 may have no antihalation layer. They look the same both sides:
5302 looks like white translucent plastic and 5360 looks like red
transparent plastic. I seem to recall that you can expose either
side, though you obviously want emulsion-to-emulsion for contact
printing.

Also, the back coating is also used for
countering the curling tendency of the emulsion the
anti-halation dye is usually included in this coating. If
there is no back coating at all I suspect the film will curl
very badly.

For all its faults, the Lucky film curls no more than usual.

FWIW normal emulsion is nearly transparent, this is why
special motion picture effects could be made by bipacking
(running two films through the camera emulsion to emulsion
and exposing through the back of one of them).

The Lucky film is grey and somewhat translucent and looks the same
colour from both sides. If you put undeveloped film on a newspaper
you could probably just manage to read through it. If you had a light
behind the paper it would be easy. Transparent suggests to me
something like 5360 which looks like nearly clear red plastic - so much so
that I had some trouble believing that it was actual film when
I first saw what looked to be clear film under a red safelight.

Peter.
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