Post by John Duncan on Nov 1, 2022 14:34:04 GMT -5
Exposing The Photographic Panel
by Herbert Blenner 6/2001
The photographic panel put salesmanship ahead of scholarship and replaced analysis by synthesis. The photographic panel of the HSCA evaluated the backyard photos. They employed various photo analytic techniques. However, their vanishing point tests produced their most compelling evidence.
In their report, the photographic panels gave a brief description of the vanishing point technique. (414) The panel correctly stated the necessity of a distant source of illumination. However, the panel had nothing to say on the second requirement of the illuminating light source.
Following the partial theoretical explanation of the vanishing point technique the photographic panel considered the methodology. (416) Here the photographic panel assumed they could draw a line through an object and the corresponding point on the object shadow. This technique, discounting measurement errors, requires the shadow has a razor-sharp edge.
When the illuminating source has no perceivable dimensions then the transition at the shadow edge is razor-sharp. We can understand this phenomenon by viewing the source of illumination from the edge of the shadow. The slightest movement at the shadow edge either totally uncovers or completely conceals the illuminating source. In other words, a razor-sharp shadow edge requires a point source of illumination.
With a finite source of illumination, such as the sun, the shadow edges are diffused. As one moves across the shadow edge, they see a changing portion of the illuminating source. This is the technicality the photographic panel overlooked in their theoretical description of the vanishing point technique.
The sharpness of the shadow edge is critical to the vanishing point analysis. When a shadow edge is diffused, the direction of a line from a point on an object through its corresponding point on the shadow edge is uncertain. Lines drawn from different objects through the corresponding points of their diffused shadow edges will fall within some small area. More than two lines will never meet at a single point.
The photographic panel found their lines met at the vanishing point. They declared the shadows were directionally consistent. (417) Then pompously proclaimed the vanishing point analysis settles the issue. (418) On this point, I have no objection.
Had the photographic panel faithfully analyzed the backyard photos they would have found their lines passing through some small area. This result would show directionally consistency of the shadows. Nevertheless, the photographic panel substituted synthesis for analysis. They drew their lines through a fictitious vanishing point that intersected points on objects and fell near the diffused shadow edges.
The photographic panel cheated on the vanishing point test. They did this under the mistaken belief that directionally consistency of shadows from the sun required lines to met at a common point. Thanks to a technical oversight, the photographic panel gives us proof they mishandled the evidence.
Source: Volume VI of the House Select Committee on Assassinations.
The following references are from section B, Photograph Authentication:
(414) The consistency of the shadows was also evaluated by application of the vanishing point principle. The concept of "vanishing point" perspective is widely known with respect to artists and applies to photography as well. (178) This concept simply means that parallel lines in object space are depicted as converging lines on the image which will eventually meet at a point. Because the Sun's distance from Earth is so great that it may be considered infinitely distant, it follows that, in any sunlit scene, lines from objects to their shadows are parallel. When these parallel lines are pictured the corresponding lines on the picture converge at a point known as the vanishing point. A picture of parallel railroad tracks provides a good illustration; the tracks are seen to converge to a point at the horizon.
(415) In the case of the railroad tracks, the vanishing point is in the picture. This may not always occur. If the lines are perpendicular to the camera axis (the line from the center of the lens to the center of the film), the images of the lines will not appear to converge at a point, on the picture. The vanishing point may then be considered to be at infinity. In other cases, where the parallel lines are not perpendicular to the camera axis, the vanishing point is either in the picture or some finite distance outside it.
(416) When this is the case, the directional consistency of shadows may be tested by drawing lines from images of objects to the corresponding points on the images of their shadows, and then extending these lines (beyond the actual picture if necessary) to see if they are meet at one point. If the lines do meet at one point, they are parallel and therefore consistent. If they do not met at one point, they are not parallel and consequently are not consistent.
(417) When this analysis was applied to the backyard prints by drawing lines from a part of the stairway, the butt of Oswald's pistol, the muzzle of the rifle, Oswald's nose, et cetera, to the corresponding points on the shadows cast by these objects, the lines all met at the vanishing point. (See figs. IV-34 and IV-35, JFK exhibits Nos. F-387 and F-388.) Accordingly, the shadows were determined to he directionally consistent. A vanishing point analysis on 133C(Stovall) also yielded consistent results.
(418) While the vanishing point analysis settles this issue, comparisons between shadows depicted in different backyard pictures cannot be validly made unless the illumination, precise geometry of the head and the exact location of the camera are considered. It is for this reason that the allegation of fakery, based on the observation that a shadow has not moved between pictures despite movement of the object casting it, is fundamentally misconceived. The argument fails to account for the compensating effect of movement by the camera.(179) This principle is illustrated in the RIT Technical Report, pars. 470-74 infra.
by Herbert Blenner 6/2001
The photographic panel put salesmanship ahead of scholarship and replaced analysis by synthesis. The photographic panel of the HSCA evaluated the backyard photos. They employed various photo analytic techniques. However, their vanishing point tests produced their most compelling evidence.
In their report, the photographic panels gave a brief description of the vanishing point technique. (414) The panel correctly stated the necessity of a distant source of illumination. However, the panel had nothing to say on the second requirement of the illuminating light source.
Following the partial theoretical explanation of the vanishing point technique the photographic panel considered the methodology. (416) Here the photographic panel assumed they could draw a line through an object and the corresponding point on the object shadow. This technique, discounting measurement errors, requires the shadow has a razor-sharp edge.
When the illuminating source has no perceivable dimensions then the transition at the shadow edge is razor-sharp. We can understand this phenomenon by viewing the source of illumination from the edge of the shadow. The slightest movement at the shadow edge either totally uncovers or completely conceals the illuminating source. In other words, a razor-sharp shadow edge requires a point source of illumination.
With a finite source of illumination, such as the sun, the shadow edges are diffused. As one moves across the shadow edge, they see a changing portion of the illuminating source. This is the technicality the photographic panel overlooked in their theoretical description of the vanishing point technique.
The sharpness of the shadow edge is critical to the vanishing point analysis. When a shadow edge is diffused, the direction of a line from a point on an object through its corresponding point on the shadow edge is uncertain. Lines drawn from different objects through the corresponding points of their diffused shadow edges will fall within some small area. More than two lines will never meet at a single point.
The photographic panel found their lines met at the vanishing point. They declared the shadows were directionally consistent. (417) Then pompously proclaimed the vanishing point analysis settles the issue. (418) On this point, I have no objection.
Had the photographic panel faithfully analyzed the backyard photos they would have found their lines passing through some small area. This result would show directionally consistency of the shadows. Nevertheless, the photographic panel substituted synthesis for analysis. They drew their lines through a fictitious vanishing point that intersected points on objects and fell near the diffused shadow edges.
The photographic panel cheated on the vanishing point test. They did this under the mistaken belief that directionally consistency of shadows from the sun required lines to met at a common point. Thanks to a technical oversight, the photographic panel gives us proof they mishandled the evidence.
Source: Volume VI of the House Select Committee on Assassinations.
The following references are from section B, Photograph Authentication:
(414) The consistency of the shadows was also evaluated by application of the vanishing point principle. The concept of "vanishing point" perspective is widely known with respect to artists and applies to photography as well. (178) This concept simply means that parallel lines in object space are depicted as converging lines on the image which will eventually meet at a point. Because the Sun's distance from Earth is so great that it may be considered infinitely distant, it follows that, in any sunlit scene, lines from objects to their shadows are parallel. When these parallel lines are pictured the corresponding lines on the picture converge at a point known as the vanishing point. A picture of parallel railroad tracks provides a good illustration; the tracks are seen to converge to a point at the horizon.
(415) In the case of the railroad tracks, the vanishing point is in the picture. This may not always occur. If the lines are perpendicular to the camera axis (the line from the center of the lens to the center of the film), the images of the lines will not appear to converge at a point, on the picture. The vanishing point may then be considered to be at infinity. In other cases, where the parallel lines are not perpendicular to the camera axis, the vanishing point is either in the picture or some finite distance outside it.
(416) When this is the case, the directional consistency of shadows may be tested by drawing lines from images of objects to the corresponding points on the images of their shadows, and then extending these lines (beyond the actual picture if necessary) to see if they are meet at one point. If the lines do meet at one point, they are parallel and therefore consistent. If they do not met at one point, they are not parallel and consequently are not consistent.
(417) When this analysis was applied to the backyard prints by drawing lines from a part of the stairway, the butt of Oswald's pistol, the muzzle of the rifle, Oswald's nose, et cetera, to the corresponding points on the shadows cast by these objects, the lines all met at the vanishing point. (See figs. IV-34 and IV-35, JFK exhibits Nos. F-387 and F-388.) Accordingly, the shadows were determined to he directionally consistent. A vanishing point analysis on 133C(Stovall) also yielded consistent results.
(418) While the vanishing point analysis settles this issue, comparisons between shadows depicted in different backyard pictures cannot be validly made unless the illumination, precise geometry of the head and the exact location of the camera are considered. It is for this reason that the allegation of fakery, based on the observation that a shadow has not moved between pictures despite movement of the object casting it, is fundamentally misconceived. The argument fails to account for the compensating effect of movement by the camera.(179) This principle is illustrated in the RIT Technical Report, pars. 470-74 infra.