Post by John Duncan on Dec 2, 2022 18:49:10 GMT -5
Backyard Photographs -- Scratch Marks
by Herbert Blenner 10/2003
2.bp.blogspot.com/-HPQnsOqQfnY/Tmel8ssSYOI/AAAAAAAAhTc/hQBiAfX1ZpA/s530/Oswald-Backyard-Photos.jpg
Negative scratch marks in precisely the same location on all backyard photo materials provide evidence of fakery.
Dr. Leslie Stroebel, Mr. Andrew Davidhazy, and Dr. Ronald Francis of the Photographic Panel exposed a roll of film in the Imperial Reflex camera and studied the camera signature. They found distinctive marks with variations of minor details. (450) Further comparison of their negatives with CE 749, the original negative of CE 133B, showed sufficient similarities of signatures to establish an important point. (448) Namely the distinctive features of the Imperial Reflex camera signature remained essentially unchanged during fifteen years.
Documenting the variations of minor details was important for an unobvious reason. A camera being a machine has slight variations in its movements. So a camera never exactly reproduces its signature. Likewise the same manufacturing machine produces cameras with slightly differing signatures. Without recognition of this omnipresent variability of machines, the basis for linking photographic materials to a particular camera collapses.
Analysis of the Imperial Reflex camera and all the backyard photographic materials by another HSCA group produced conflicting results. This group exposed rolls of film in the Imperial Reflex camera and after development examined frame edge markings and scratch marks. They found unchanging camera signatures. (391)
This result is shocking because careful examination of a roll of film by Dr. Leslie Stroebel, Mr. Andrew Davidhazy, and Dr. Ronald Francis showed considerable variations of camera signatures.(450) The implications of this being those who found unchanging camera signatures were careless in each repeat of their experiment.
More troublesome and consequential problems arise from the report of this group on their scratch mark analysis of all the backyard photographic materials. They found "scratch marks were located in precisely the same location in each photograph." (394)
The examined materials contained one original negative, several prints and enlargements of varying sizes. This assortment precluded a causal examination. Differences in sizes of these materials demanded a rigorous analysis. Under these circumstances failure to notice and report minor variations of camera signatures is inexcusable.
Either this group abused language and produced a misleading report with intention to deceive or they observed irrefutable evidence of fakery. In this latter case, forgers would have used a single signature of the Imperial Reflex camera to impress upon the backyard photo negatives that were produced by precision equipment.
This technique of forgery is tedious. They require many photographic, masking, and etching steps to produce a single forged signature. These complications explain why the forgers took a shortcut and used the same forged signature for each backyard photograph.
Candid investigators could have detected this means of forgery by comparing variations of camera signatures on the backyard photo negatives with variations measured on their test negatives. They would find no evidence of this kind of forgery on backyard photo negatives whose signature variations were comparable with those of their test negatives. Only by finding significantly less or absence of signature variations on the backyard negatives could investigators conclude fakery by photographic impression of a common camera signature. Of course finding the missing negative of CE 133-A was a prerequisite for testing.
Measurement of signature variations from photographs is tedious. The negative scratch marks reside on a layer beneath a transparent protective coating. During handling this protective coating gets scratched. Separation of emulsion from negative scratch marks is one complication.
A high-powered microscope could focus upon the negative scratch marks and its short depth of focus would render emulsion marks invisible. However this technique requires precision three-axis positioning tables for both photographs.
Further the varying sizes of the backyard photos along with the dimensional instability of photographic paper (452) necessitated number crunching ability. Clearly solving these problems in 1978 required building a custom data acquisition and processing system.
Source: HSCA Photographic Panel Report:
(391) In order to determine the pattern of these camera signatures the case of CE 750, Oswald's Imperial Reflex camera, test photographs were made with it and then intentionally underexposed in development to show the frame edge markings better. (No special development method was necessary to bring out the camera scratch mark pattern.) (See fig. IV-26, JFK exhibit No. F-190). Each time the film was run through the camera, the camera signature created by the frame edge markings and scratch marks was found to be the same. (165)
(394) These results were confirmed by the panel's scratch-mark analysis. Here, all the backyard picture materials could be reviewed because the scratch marks that were the subject of the analysis had not been cropped out by any of the prints' white borders. The analysis clearly indicated that the scratch marks were located in precisely the same location in each photograph. (See figs. IV-26, 28, and 29.) (169)
(448) When negatives that were exposed in the Oswald camera by the undersigned were compared with the negative of Oswald, similarities in the edge markings from irregularities in the film aperture and scratch patterns indicated that the negative of Oswald was exposed in the Oswald camera. In addition, variations in sharpness from the center to the edges, and pincushion distortion were similar on the original and comparison negatives.
(450) We had intended to make a quantitative comparison of the edge markings on the various photographs, as suggested by a panel member, by aligning parts of edge markings, measuring the displacement at fixed intervals and calculating the standard deviation. Careful examination of a roll of film we exposed in the Oswald camera revealed that while the distinctive marks appeared consistently on each frame of film, the straightness of the lines varied considerably-apparently due to slight buckling of the film. Instead, we made prints that compare pairs of edges on all four sides of the picture frame.
(452) There are two obvious discrepancies that we consider to be insignificant. (1) When one edge of the two images is aligned, there is a slight lack of parallelism on the other three edges. Since the two prints were made with two different enlargers, any deviation from exact parallelism of the negative and the easel on either enlarger, a not uncommon defect in enlargers, would produce this effect. (2) There is an obvious difference in the vertical to horizontal proportions of the two images. The dimensional stability of photographic paper during processing and drying is different in the direction of the paper grain as opposed to across the paper grain. The difference in proportions is consistent with expectations if the paper grain were oriented vertically on one print and horizontally on the other.
by Herbert Blenner 10/2003
2.bp.blogspot.com/-HPQnsOqQfnY/Tmel8ssSYOI/AAAAAAAAhTc/hQBiAfX1ZpA/s530/Oswald-Backyard-Photos.jpg
Negative scratch marks in precisely the same location on all backyard photo materials provide evidence of fakery.
Dr. Leslie Stroebel, Mr. Andrew Davidhazy, and Dr. Ronald Francis of the Photographic Panel exposed a roll of film in the Imperial Reflex camera and studied the camera signature. They found distinctive marks with variations of minor details. (450) Further comparison of their negatives with CE 749, the original negative of CE 133B, showed sufficient similarities of signatures to establish an important point. (448) Namely the distinctive features of the Imperial Reflex camera signature remained essentially unchanged during fifteen years.
Documenting the variations of minor details was important for an unobvious reason. A camera being a machine has slight variations in its movements. So a camera never exactly reproduces its signature. Likewise the same manufacturing machine produces cameras with slightly differing signatures. Without recognition of this omnipresent variability of machines, the basis for linking photographic materials to a particular camera collapses.
Analysis of the Imperial Reflex camera and all the backyard photographic materials by another HSCA group produced conflicting results. This group exposed rolls of film in the Imperial Reflex camera and after development examined frame edge markings and scratch marks. They found unchanging camera signatures. (391)
This result is shocking because careful examination of a roll of film by Dr. Leslie Stroebel, Mr. Andrew Davidhazy, and Dr. Ronald Francis showed considerable variations of camera signatures.(450) The implications of this being those who found unchanging camera signatures were careless in each repeat of their experiment.
More troublesome and consequential problems arise from the report of this group on their scratch mark analysis of all the backyard photographic materials. They found "scratch marks were located in precisely the same location in each photograph." (394)
The examined materials contained one original negative, several prints and enlargements of varying sizes. This assortment precluded a causal examination. Differences in sizes of these materials demanded a rigorous analysis. Under these circumstances failure to notice and report minor variations of camera signatures is inexcusable.
Either this group abused language and produced a misleading report with intention to deceive or they observed irrefutable evidence of fakery. In this latter case, forgers would have used a single signature of the Imperial Reflex camera to impress upon the backyard photo negatives that were produced by precision equipment.
This technique of forgery is tedious. They require many photographic, masking, and etching steps to produce a single forged signature. These complications explain why the forgers took a shortcut and used the same forged signature for each backyard photograph.
Candid investigators could have detected this means of forgery by comparing variations of camera signatures on the backyard photo negatives with variations measured on their test negatives. They would find no evidence of this kind of forgery on backyard photo negatives whose signature variations were comparable with those of their test negatives. Only by finding significantly less or absence of signature variations on the backyard negatives could investigators conclude fakery by photographic impression of a common camera signature. Of course finding the missing negative of CE 133-A was a prerequisite for testing.
Measurement of signature variations from photographs is tedious. The negative scratch marks reside on a layer beneath a transparent protective coating. During handling this protective coating gets scratched. Separation of emulsion from negative scratch marks is one complication.
A high-powered microscope could focus upon the negative scratch marks and its short depth of focus would render emulsion marks invisible. However this technique requires precision three-axis positioning tables for both photographs.
Further the varying sizes of the backyard photos along with the dimensional instability of photographic paper (452) necessitated number crunching ability. Clearly solving these problems in 1978 required building a custom data acquisition and processing system.
Source: HSCA Photographic Panel Report:
(391) In order to determine the pattern of these camera signatures the case of CE 750, Oswald's Imperial Reflex camera, test photographs were made with it and then intentionally underexposed in development to show the frame edge markings better. (No special development method was necessary to bring out the camera scratch mark pattern.) (See fig. IV-26, JFK exhibit No. F-190). Each time the film was run through the camera, the camera signature created by the frame edge markings and scratch marks was found to be the same. (165)
(394) These results were confirmed by the panel's scratch-mark analysis. Here, all the backyard picture materials could be reviewed because the scratch marks that were the subject of the analysis had not been cropped out by any of the prints' white borders. The analysis clearly indicated that the scratch marks were located in precisely the same location in each photograph. (See figs. IV-26, 28, and 29.) (169)
(448) When negatives that were exposed in the Oswald camera by the undersigned were compared with the negative of Oswald, similarities in the edge markings from irregularities in the film aperture and scratch patterns indicated that the negative of Oswald was exposed in the Oswald camera. In addition, variations in sharpness from the center to the edges, and pincushion distortion were similar on the original and comparison negatives.
(450) We had intended to make a quantitative comparison of the edge markings on the various photographs, as suggested by a panel member, by aligning parts of edge markings, measuring the displacement at fixed intervals and calculating the standard deviation. Careful examination of a roll of film we exposed in the Oswald camera revealed that while the distinctive marks appeared consistently on each frame of film, the straightness of the lines varied considerably-apparently due to slight buckling of the film. Instead, we made prints that compare pairs of edges on all four sides of the picture frame.
(452) There are two obvious discrepancies that we consider to be insignificant. (1) When one edge of the two images is aligned, there is a slight lack of parallelism on the other three edges. Since the two prints were made with two different enlargers, any deviation from exact parallelism of the negative and the easel on either enlarger, a not uncommon defect in enlargers, would produce this effect. (2) There is an obvious difference in the vertical to horizontal proportions of the two images. The dimensional stability of photographic paper during processing and drying is different in the direction of the paper grain as opposed to across the paper grain. The difference in proportions is consistent with expectations if the paper grain were oriented vertically on one print and horizontally on the other.