Custom frame size on old 8mm films

[DavidOP]

My question is about 8mm film, specifically the famous Zapruder fillm (motion but no sound). It was made with 8mm camera on 16mm film. The standard size of 8mm frame is 3.68 x 4.88mm. But it seems like the frames in Zapruder film are 3.68 x 6.58mm. This means the camera had to have some custom setting with lens aperture to allow the larger image to reach the film, around the intersprocket area.

How common was to have a retail camera (high end amateur model) to have such special setting? As far as I know the lens was permanently fixed to the camera, so it had to be done at factory or some professional shop. How common was it in the 60s? Why would anybody want to have it since most projectors would not even display beyond the standard frame size anyway?

 

[compur]

Frame size of standard 8 mm film is 4.8 mm x 3.5 mm. It was shot on a 16mm wide roll of film exposing only one half of the width of the film. At the end of the roll it was flipped over and shot again, exposing the other half. When processed the film was split down the middle and the 2 halves spliced together to make one roll of 8mm for projection.

See:
8 mm film - Wikipedia, the free encyclopedia

But it seems like the frames in Zapruder film are 3.68 x 6.58mm.

How did you determine those dimensions?

 

[DavidOP]

My mistake. I put the size of aperture, and not the frame. The standard frame size is 3.5mm x 4.8mm.

Look at one frame from Zapruder film, frame 312.

http://assassinationresearch.com/zfilm/z312.jpg

like all other frames, this frame shows aspect 1.79. Take any software program that lets you measure the pixels of selected area, and measure the horiz and vertical distances of the frame.
horiz = 816 pixels
vert = 456 pixels

i.e. aspect 816/456 = 1.79

since the vertical is fixed, you can compute the horiz as 3.5x1.79=6.27mm versus the standard 4.8mm

this means that the aperture is non-standard, i.e. custom made. My question is how come there is a custom aperture on a amateur model. Was it normal in the 1960s?

 

[compur]

My question is how come there is a custom aperture on a amateur model. Was it normal in the 1960s?

No, customizing frame or aperture dimensions on movie cameras was not common.

 

[Helen B]

The film gate (aperture plate) must have been open on the sprocket side, probably to clear the claw in a compact arrangement. This must have been normal for that camera. The standard size image would have been projected, so the part of the image between the sprockets would not be seen. If you were really interested in that you might want to try locating the optical axis. It should be in the dead centre of the standard frame.

 

[DavidOP]

The image reaches the intersprocket area only when the telephoto setting is used because its exit window is wider. If the intersprocket area is not covered by anything, then the projected image falls on the exposed film. So the question can be stated more clearly. Is this a design intent, or somebody was messing with the camera inside to make the intersprocket area exposed as a custom feature?

The next question is why the part of image that falls onto the intersprocket area is recorded on the film? Does it make any sense to have an emulsion on the film around the intersprocket area. It sounds like waste of money during manufacturing process. More emulsion, more silver required, and more costs. Was it normal for a film to have emulsion extending over the standard format? It is fine vertically between frames, but horizontally into the sprocket area is a total waste of money. Did all 16mm films have this issue, or only special versions?

 

[compur]

The next question is why the part of image that falls onto the intersprocket area is recorded on the film? Does it make any sense to have an emulsion on the film around the intersprocket area. It sounds like waste of money during manufacturing process. More emulsion, more silver required, and more costs. Was it normal for a film to have emulsion extending over the standard format? ?

Yes, it was and still is normal to have emulsion in the sprocket area of many types of film. How this affects cost of manufacture I can't say for sure. My guess is that the cost of selectively coating only the intended image area of a film may be more than would be saved by using less emulsion.

 

[Helen B]

The image reaches the intersprocket area only when the telephoto setting is used because its exit window is wider. If the intersprocket area is not covered by anything, then the projected image falls on the exposed film. So the question can be stated more clearly. Is this a design intent, or somebody was messing with the camera inside to make the intersprocket area exposed as a custom feature?

The next question is why the part of image that falls onto the intersprocket area is recorded on the film? Does it make any sense to have an emulsion on the film around the intersprocket area. It sounds like waste of money during manufacturing process. More emulsion, more silver required, and more costs. Was it normal for a film to have emulsion extending over the standard format? It is fine vertically between frames, but horizontally into the sprocket area is a total waste of money. Did all 16mm films have this issue, or only special versions?

As I already mentioned, the film is not covered because the claw requires empty space in front of the film. If the claw is beside the image, then the image may be recorded in the intersprocket area. It has nothing to do with any intention to record more of the lens' image circle.

Film is made in wide rolls which are later cut down into narrower widths. It is not made at the width it will be when it goes through a camera.