The claim I am offering herein, that Roger Patterson had a 15mm lens on his camera that day at Bluff Creek, will be subjected to rigorous examination and challenge by others in the coming months. I anticipate this and given the potential of how it reframes the whole discussion of the subject in the film, it should be challenged and examined by as many people as possible, people who have technical expertise to determine the fact or error in the claim.
My goal here is to offer up as much supporting material as I now have, and continue to add to it in the coming months, so that others have as much data to test and evaluate as possible. This section presents both the general concept foundation ideas anyone evaluating this issue should be aware of, first, and then explains specifics that I have done or considered in my analysis.
The K-100 Camera - This camera is a spring-driven standard 16mm camera which takes a 100' daylight load of film stock. In its standard configuration, it holds one lens for the camera proper, and a companion lens for the side viewfinder. It is not equipped for viewing through the camera lens. In general principle, this restricts the camera to using the lenses supplied by Kodak, with their companion viewfinder lenses, and precludes the prospect of using a zoom lens. This is not a mechanical restriction, so much as question of reason and intent to use the camera successfully.
Mechanically, the camera accepts lenses with a "C" mount, and also an "S" mount with an adapter (Kodak's 15mm lens for this camera is an "S" mount, with a Kodak-made adapter for "S" to "C" mount attached, as one example). So in theory, any "C" mount lens can be put on the camera, and should render an acceptable picture. But if you do not have the companion viewfinder lens, then what you see in the viewfinder is not the composition you get on the film. So we must ask, what logical purpose would a camera user anticipate to deliberately configure the camera to insure what he/she sees in the viewfinder is guaranteed NOT TO BE what will result on film?
And when you consider the camera was a rental, what would motivate the rental person to even allow the renter to take out the camera under these circumstances, when the resulting footage, not to the camera user's liking, could put the blame on the rental company for failing to equip the camera properly with the correctly matching camera and viewfinder lens pair?
So on this issue, one can argue for the mechanical possibility of using any "C" mount lens on the camera and successfully filming, but in the practical sense, the sheer irrationality of using a camera and viewfinder lens pair that are deliberately mismatched in focal length, suggests to me the prospect is unlikely and testing for this is simply not a high priority in my research effort. Far more likely and probable things have priority for my research time. So with this in mind, I have given priority to the Kodak 25mm lens and the Kodak 15mm lens that do have companion viewfinder lens available for that camera. Other researchers may, of course, test for lenses of other focal lengths, if they feel that the effort is a worthwhile pursuit.
There will continue to be arguments that the camera used by Roger for the PG Film had the 25mm lens on it, because rental documents and some type of police report (when he apparently failed to return it in a timely manner) specify a 25mm lens on those documents. It is reasonable to say, when he rented it, months before, it did have a 25mm lens on it. But changing a lens requires about one minute of time, and so the prospect that he changed lenses on the camera somewhere between the time of the rental and the filming at Bluff Creek is a perfectly reasonable expectation. And from an argumentative standpoint, the 15mm lens is a better lens for scenic outdoor photography, and that is substantially what Roger had been filming in the months he had the camera.
Ultimately, however, the lens determination must be made by optical science and mathematics, not arguments of speculated human behavior. So while all the above notes are relevant to the discussion, they are not being used in any proof of the lens focal length.
Verifying the Lens
There are several approaches to verifying the lens used on Roger's camera. The methods I am intending to use in this analysis are Replication, Mathematical Model, and Photogrammetry Software Processing.
Replication - This is the process of duplicating the process of filming, with a model or mockup of the original scene of Bluff Creek, using specified camera positions and lens specifications to correspond to specific frames of the real film. The greater the number of camera positions used, and the greater the number of objects which match in position and size, the greater the likelihood that the replication is a truthful determination. An example, in ballistics, would be to look at a bullet slug recovered from a crime scene, and studying the bullet deformation from impact, and then replicate the event by firing the same type bullet into various physical substances to study the deformations on impact of the study bullets, as compared to the deformations of the crime scene bullet. A replication of deformation argues for the study criteria as being consistent with the crime scene criteria.
In this case, a digital model has been constructed of the Bluff Creek site, and matched to seven film frames representing seven different camera positions. And 15 objects, most representing multiple points (which allows for comparing both their position and size relative to the objects in the film images), have been used. A score sheet charting the points or objects which match in varied film frames has been developed, and a full data sheet of object coordinates (dimension, position and rotation) has been provided for other researchers to test the model independently. Camera coordinates (position and rotation) have also been provided.
This replication method first allows me to compare my site model to the film, and determine that an excellent match of objects and camera positions occurs for the lens specification I am testing (the 15mm lens), and also allows for other researchers to replicate my efforts independently and verify the results. It further provides both myself and other researchers with the materials to test other lens specifications with similar model replication, by adjusting the lens angle of view, and them setting different camera and object positions to attempt an alternate replication where we can grade the number of matches. If they do so, their results can be easily documented in a consistent manner for other researchers and myself to verify.
Mathematical Model - A mathematical model should allow for calculations of object positions and camera positions based entirely on the object position and dimension data that can be extracted from the film. This mathematical model should allow for exact computations of relative position of objects and cameras, independent of a viewing angle, so it can be done without a pre-determined lens angle of view put into the process (as the replication method does require). So this method, once accomplished, would be an independent verification of the lens, determined after the mathematical model is complete. Work is currently underway to define the various tree objects in the highest quality image form, as they appear in multiple frames, so the data has a high degree of accuracy and a low margin of error.
Once the data is prepared for this method, it will be released for independent researchers to evaluate and test.
Photogrammetry Software Analysis - Software which performs photogrammetry analysis uses an automated version of the mathematical model described above, with specific algorithms developed first to analyze film footage and  identify points, objects or patterns (like pattern recognition or edge detection methods), and then additional algorithms to process the data and determine point positions, camera positions and lens focal length. I have been using one product, boujou 4.1 made by 2D3 Ltd of the UK, for this method. The boujou software is a CGI industry "Matchmove" software which specifically tracks points, objects, cameras and lens data so a digital model or effect can be composited into real film footage effectively. I chose it specifically for its capability of locating cameras and determining lens focal lengths.
A preliminary analysis I have done confirmed the 15mm lens on the PG Film camera, and a separate test using footage I generated with a known lens horizontal field of view was tested by the software and determined to be accurate in its lens determination. I am currently running additional tests with more footage, as well as setting up the PG Film frames for a more lengthy and detailed analysis, which I will document thoroughly. The staff of the software developer have also graciously offered to run their own analysis using the footage, and preparations for that effort are being made.
Links To Lens Data
The following pages will go to the various discussions and image documents which show the Replication with the Digital Site Model, and provide more information about the process. Additionally, some links will go to the material other researchers will need to test the Digital Model.
Foundation Data on the Model Visualizaion Software                   Camera Data                 Model Data
Actual Replications illustrated:     C3      C4A     C4B    C5     C6     C7     C8     Byrne      Dahinden
The Model Data Sheets          Bryce Model Data     Image Panel Data        Blank Form       
                                               Other Camera Data      Measurement Bars Data
The Site Model and measurements     The Height Analysis and Lens Optical Formula
Comparing a Person Photographed with 15mm and 25mm Lens
Photogrammetry Process notes                 Conclusion          
Website Index         Overview Navigation Page
Verification and Falsification - A correct proof needs both verification and falsification to be complete. Verification is the positive or proactive demonstrating or determination that the fact claimed is correct. Falsification is the demonstration that alternatives cannot be correct. Both are considered strongest in factual certainty when results are replicated by persons other than the claimant of the proof. So I am making the data available for other researchers with that intent, that they may test the models and data, and either concur or contest the results I have obtained.
My primary verification of the 15mm lens claim at this point is the replication, and the high number of matches in multiple objects and multiple camera positions. The compatability of the camera position determinations as compared to site map measurement data and other filming at the site is supportive of this claim. What is currently lacking is the margin of error calculation, still under study.
My primary falsification of the 25mm lens (thus far) is that after two months of attempting to build a digital model of Bluff Creek using the 25mm specifications, the model failed to solve by every effort or method. But at the time I was doing so, I wasn't thinking in terms of trying to falsify the 25mm lens. I was actually trying to prove it valid. I did not maintain the appropriate documentation of the experiments, and so now, these must be redone. The work will be forthcoming, but isn't done yet.