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Old September 19th, 2017, 11:40 AM
Doug Kerr Doug Kerr is offline
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Join Date: May 2006
Location: Alamogordo, New Mexico, USA
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[Part 6]

Film magazines

The film magazines developed by Eastman Kodak were ingenious in their design.

I apologize for the illustrations used in this section. Good pictures of the innards of film magazines are hard to come by, and at this point I do not have a single magazine of either 16 mm or 8 mm size to vivisect (although an 8 mm victim is expected to arrive tomorrow).

The 16 mm film magazine

Here we see a typical Kodak 16 mm film magazine:



Kodak 16 mm film magazine
Stock photo

Here we see such a magazine opened for reloading:



Kodak 16 mm film magazine, open
Stock photo

Because the drag brake operation is disrupted with the magazine opened, the "supply" side roll of film, at the right, almost full, has unwound a bit.

The normal load of film in a 16 mm magazine is 50 feet (providing a little over 2 minutes of shot time).

This magazine has a sprocket system for governing the movement of the film. It is driven by the camera mechanism, the sprocket shaft in the magazine engaging a drive shaft in the camera. The exposure gate (aperture plate and pressure plate) are in the magazine; the intermittent motion claw is, however, in the camera proper.

We see that the interior dimensions (and the locations of the supply and takeup core spindles) are such that a full roll of film on the supply side and a full roll of film on the takeup side could not coexist - but of course, they don't have to.

The film path is fairly unique (but is in fact also found in the Ciné-Kodak Special 16 mm camera when equipped with the 100 foot capacity magazine). The first engagement of the film with the single sprocket (on its way from the supply roll to the gate) is on the bottom (as we see it) of the sprocket. The second engagement (when the film is on the way from the gate to the takeup roll) is also on the bottom of the sprocket, the two lengths of film lying one atop the other on the same sprocket teeth.

The magazine has a "footage remaining" indicator, displaying though a small window on the magazine (in turn visible through a window on the camera loading door). I have not yet been treated to a glimpse of the mechanism involved, but I presume it works from a spring-loaded finger resting on the supply roll (which no doubt also serves as the drag brake to keep the supply roll from unwinding).

The 8 mm film magazine

Here we see a typical Kodak 8 mm film magazine:



Kodak 8 mm film magazine
Stock photo

Like most 8 mm roll-loaded cameras, the 8 mm magazine uses a "double 8 mm" arrangement: the magazine is loaded with 25 feet of film 16 mm wide (but with 8 mm format perforations). The magazine is inserted in the camera and the film is run through once, laying down frames along one half of the film width. Then the magazine is removed and reinserted, other way up), and the film is run back through the camera again, laying down frames along the half of the film width.

In processing, the film is developed whole and then slit into two 25-foot lengths, which are then spliced end-to-end to give a 50 foot finished roll of film. The total shot time for a magazine is a little over four minutes.

Here we see a typical 8 mm film magazine open (it is in a Magazine Ciné-Kodak Eight camera):



Kodak 8 mm film magazine, open
Stock photo

As for the 16 mm cartridge, with the magazine open the drag brake arrangement is disrupted, and thus we see the supply roll (at the top, nearly exhausted) a bit unwound.

As with the 16 mm magazine, the exposure gate is in the magazine, and the pulldown claw is in the camera proper. The port to the exposure gate is covered by an opaque shutter until the magazine is in the camera and the loading door closed, this to minimize light leakage.

Following the lead of all but the earliest 8 mm "consumer" cameras, the 8 mm magazine system does not have any sprocket(s) to govern the movement of the film; all film moment is done by the pulldown claw.

The small "dial" we see in the earlier picture of this magazine is, sadly, not an actual "feet remaining indicator", just a picture of one. If we take the magazine out before a pass is finished (perhaps to put in a magazine with another type of film for the next task), we can mark with a pencil on this little picture the indication of the actual footage indicator (on the camera). Then, when we replace this magazine , we can set the footage indicator to match the state of the magazine so it will then correctly reflect the state of the magazine.

There is such a little picture on each side of the magazine, so from our marking we can tell which side up to put this partially-used magazine when we replace it (that is, which "pass" it was on when removed).

Best regards,

Doug
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