Re: 70mm loading

[David Josephson <david@xxxxxxxxxxxxx>]

I think most of these topics were covered in previous digests, but
having done a lot of 70mm recently, here's what I found out, in alphabetical
order...

The Alden loader is just a big version of their 35mm loader. It comes with
adapters to accept either cores or metal spools up to 100 ft size (which may
hold as much as 200 ft of thin film). It loads only the Kodak type 15 ft 
cassettes, and can be operated in daylight.

Jobo makes a 5 ft 70mm reel that fits their 2500 series tanks. This
works fine and can be loaded by hand easily. They also have a 15 ft reel
that uses a special tank and loader. It's about $600 and I have not seen one.

The Kodak cassettes are troublesome unless you pay close attention to
their assembly. It's easy to reverse the left and right caps, with the
result that the film gets scratched at the edges. Normally this wouldn't
matter, but the shards of film can settle anywhere, and sometimes this
causes the film to bind completely. Look carefully at a new cassette
and identify the left and right end caps, see how the cutout that goes
over the light trap allows the film to move all the way to the edge of
the cassette without binding if it's installed correctly. Also, when 
installed correctly the end caps go on easily with a firm snap sound; you
can force them on reversed but once you see how they work it's clear which
is right. The reason that daylight loading is discouraged is that the light 
trap fabric itself is not opaque to IR. There is an additional reason if 
you load thin Estar-based film, which pipes light more effectively than 
acetate does. 

The Linhof loading stand is, like the Alden, only for loading cassettes.
You insert the cassette spool in the cranked end and the roll of film on 
the other spindle and crank off the number of turns according to the chart
on the base. The unit must be used in the dark. There is a steel tongue
that keeps some tension on the film supply spool but it is not for guiding 
film onto a developing reel. I stick with the Linhof because it handles
400 ft spools which are the way much of the military surplus film comes.
Also it's one less trip through a potentially scratching light trap if
you load in the dark directly to a spool and *then* put the spool in the
cassette.

I have a Nikor 15 foot reel and tank. I have had no trouble loading it with
normal (0.004-0.006 inch thick) film but never got a whole roll of the 
Estar thin base film such as 3414 loaded without some kinking and sticking.
I have seen Nikor loading stands at swap meets but people wanted silly 
prices for them.

616 size film *is* 70mm and old tanks made for this size will fit. There
is a ubiquitous Spanish-made plastic tank sold under many brand names that
comes with 2 35mm-to-120 adjustable reels; I modified one of these to go
to 70mm. I also have a very old Federal tank that will take 616 film. You
can get about 5 feet of 70mm film on a 35/120 size reel or an old tank. 

There are five types of 70mm spools that I have run across so far. The
plastic spool that fits inside the Kodak cassette is the most common.
There are two 15 ft metal spools intended for darkroom loading. One has
the square and round holes on the two flanges just like a 16 or 35mm
daylight loading cine spool; the other has a larger round hole with two
keyways spaced 180 degrees on each end. This is the spool used in the KE-28
handheld aerial cameras. There is also a 50 ft version of the same spool,
and I made by KE-28 spools by cutting down the 50 ft version. Then there is
a 100 ft metal spool that looks just like a 16 or 35mm cine spool but wider.

I still have some low temperature E-4 process IR ektachrome in 70mm if
anyone wants to play with it. Hybrid E-4/E-6 process has not been
successful for me in developing this; you need E-4, ME-4 or EA-5.

- -- 
David Josephson / Josephson Engineering / San Jose CA / david@xxxxxxxxxxxxx
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