24-08-2013, 06:24 PM
You have seized upon my description of the mechanical process of the film running through the gate - which is how it was always explained during my schooling and serves as a good conceptual framework for the layman's understanding, even if slightly inaccurate - but it is not exactly relevant to the information which I am really trying to share.
With a spring-wound camera, the film does not run through the gate at a constant rate of speed. I can further say that at at a frame rate as low as 18fps, it is possible for the camera to produce artifacts such as the Greer head snap. I have seen similar artifacts working with other films.
But my skepticism to Z-film alteration theories is not limited to that. It is mostly informed by a working knowledge of optical printing.
In the late 1980s, the film co-op to which I belonged purchased an Oxberry aerial optical printer. I was there the day it arrived, and watched it be re-assembled over several days. Assembled, it is the size of a car. It remains at the co-op to this day, one of the few remaining working optical printers anywhere. Film artists have travelled to Vancouver specifically to use this machine.
I personally spent many many hours operating this printer, although never beyond simple step printing operations. People I knew were more accomplished and could do much more complex work. One of my old film professor's was a highly regarded avant-garde filmmaker who featured composite imagery created on an optical printer in many of his films. A friend of a friend came to town in the early 1990s, and in my estimation was one of the top five or so skilled optical printer technicians anywhere on the planet. There was a screening of his work, and some of the imagery was spectacular.
But of all those people and all those films I cannot recall a single shot that would have posed a technical challenge on the level of accomplishing a travelling matte featuring the limousine and its occupants as part of altering the Zapruder film. Or even removing any content, such as a head blow out. Anything removed has to be replaced with something else and I don't see any evidence of this work (except perhaps a patch on the back of the head, which many have noticed: something obviously weird there but not anywhere else). So the alterationists are supposed to not only have accomplished an extremely challenging technical feat, they have done it seamlessly.
That is half of my problem. The other half is the fact that at the end of the day one has to produce a strip of Kodachrome 8mm film -with the altered contents - which can survive expert scrutiny to plausibly serve as a camera original. And that would be the first thing I would point out if I were the technician at Hawkeye Works and was presented with this job.
Back to my American Cinematographer manual, here is information from "Exposure Control Of Optical Printers" by Mehrdad Azarmi:
"Preparation of an internegative which closely resembles the characteristics of the original has always been the goal of optical houses throughout the industry. In spite of the superb quality frequently achieved in internegatives, it seems virtually impossible to attain characteristics identical to those of the original negative in the duplicate generations for the following reasons:
1. The non-linear response of photographic film limits the range over which the following generations can duplicate an original. The internegative is one or two generations away from the original, depending on the stock used.
2. Many variable elements are introduced during the processing of the internegative.
3. The exposure characteristics of the optical printer may vary from time to time.
With a spring-wound camera, the film does not run through the gate at a constant rate of speed. I can further say that at at a frame rate as low as 18fps, it is possible for the camera to produce artifacts such as the Greer head snap. I have seen similar artifacts working with other films.
But my skepticism to Z-film alteration theories is not limited to that. It is mostly informed by a working knowledge of optical printing.
In the late 1980s, the film co-op to which I belonged purchased an Oxberry aerial optical printer. I was there the day it arrived, and watched it be re-assembled over several days. Assembled, it is the size of a car. It remains at the co-op to this day, one of the few remaining working optical printers anywhere. Film artists have travelled to Vancouver specifically to use this machine.
I personally spent many many hours operating this printer, although never beyond simple step printing operations. People I knew were more accomplished and could do much more complex work. One of my old film professor's was a highly regarded avant-garde filmmaker who featured composite imagery created on an optical printer in many of his films. A friend of a friend came to town in the early 1990s, and in my estimation was one of the top five or so skilled optical printer technicians anywhere on the planet. There was a screening of his work, and some of the imagery was spectacular.
But of all those people and all those films I cannot recall a single shot that would have posed a technical challenge on the level of accomplishing a travelling matte featuring the limousine and its occupants as part of altering the Zapruder film. Or even removing any content, such as a head blow out. Anything removed has to be replaced with something else and I don't see any evidence of this work (except perhaps a patch on the back of the head, which many have noticed: something obviously weird there but not anywhere else). So the alterationists are supposed to not only have accomplished an extremely challenging technical feat, they have done it seamlessly.
That is half of my problem. The other half is the fact that at the end of the day one has to produce a strip of Kodachrome 8mm film -with the altered contents - which can survive expert scrutiny to plausibly serve as a camera original. And that would be the first thing I would point out if I were the technician at Hawkeye Works and was presented with this job.
Back to my American Cinematographer manual, here is information from "Exposure Control Of Optical Printers" by Mehrdad Azarmi:
"Preparation of an internegative which closely resembles the characteristics of the original has always been the goal of optical houses throughout the industry. In spite of the superb quality frequently achieved in internegatives, it seems virtually impossible to attain characteristics identical to those of the original negative in the duplicate generations for the following reasons:
1. The non-linear response of photographic film limits the range over which the following generations can duplicate an original. The internegative is one or two generations away from the original, depending on the stock used.
2. Many variable elements are introduced during the processing of the internegative.
3. The exposure characteristics of the optical printer may vary from time to time.