Notes on the PGF Lens Analysis
In 2008, I began my intense evaluation of the PGF. Before that, I had a passing interest in it, like so many other people, but I was not immersed in the details and was not engaged in discussions and debates.
But once I did begin to give extensive and serious consideration to this film, I realized the issues and controversies were vast and the evidence was overwhelming in terms of volume. I also soon realized that the PGF story was hurt by a multitude of mistaken assumptions passing for facts, and for poor evidence passing for good.
My concern for the type of lens used on Roger Pattersonís camera came from a suspicion that the best solution for calculating the filmed subjectís height was to use the classic lens optics formula which shows the relationship between four variables, the lens focal length, the measured distance from camera to subject, the subjectís real size, and the subjectís image size on film. With a basic understanding of how various lenses can compress the 3D space into 2dimensions and produce different proportional relationships between the objects in the scene, I began to develop a sense that the lens on the PGF camera may possibly be wider than the 25mm lens commonly described and assumed.
In exploring this issue, I assumed that the lens would likely be one of those made by Kodak for the K-100 camera so there was an equal focal length view eyepiece lens as a companion. The only lens wider than the standard 25mm which had such a companion viewer lens was the 15mm. In my original analysis notes, I did acknowledge that a ďC Mount" lens of any focal length could be put on the K-100 camera, even if there was no companion viewer lens, and the camera would capture a fine image. But the camera operator canít see exactly what heís filming if his viewer lens and camera taking lens are not matched in focal length. The operator may see much more than the film captures, or see less. A camera operator can do this, but I found it seemed like an odd way to configure his camera, so I gave my attention to the more logical configuration of using a wide angle lens which has an equal focal length viewer lens as well. That made the likely candidate to test a 15mm lens.
I did build a computer model with both a 25mm lens and a 15mm lens specification, trying to reconstruct the Bluff Creek landscape and arrangement of objects, and the 15mm model worker better.
In May of 2009, at an event honoring Bob Gimlin,I made my announcement about the 15mm lens and why I felt it was more likely than a 25mm lens to be used on Pattersonís camera. I also launched this website with a lot of supporting information on my effort to analyze this. What I had not counted on were two things: One was that there are more variables in the solution than my first appraisal of the problem indicated; and Two, I was completely unprepared for how powerful the internet is in spreading information and how helpless we are to try and correct something in error once it has spread.
Good science requires that we challenge our own work, even as we challenge the analysis of others, and we must be willing to reconsider our conclusions if new data or new considerations are brought into the matter. But people  intent on arguing and winning arguments take any change, revision or re-appraisal as a weakness, when in true classical searches for truth, it is always a strength, an asset. I chose the science path, being willing to see my own need for reconsideration of my effort, and being willing to say so publicly and sincerely. As new data (particularly some new and high quality scans from John greenís filming of Jim McClarin at Bluff Creek) was analyzed, I found the 15mm lens was now problematic, but that the 25mm lens option still unlikely.
So I simply and sincerely started announcing that I would review the whole lens matter, put all lens options back on the table, and factor in the new data and variables. But the initial announcement of the 15mm lens had already started making the rounds of the internet, and had been featured on a MonsterQuest TV program, and I had no capacity to revise or edit either media descriptions.
It was an awkward lesson to learn, and I know my critics like to paint it as a failure. But real scientific investigation does have such things occurring, and the responsible thing is to not hide the original analysis that proved in error, but rather learn from it as a motivation to revise the analysis with greater caution, consideration for all variables and invite the participation of other experts to cross-check the effort.
The work is not done yet, because some of the tests and analysis effort need funding I have not secured yet. But I have written about the issue in the PDF specifically comparing John Greenís filming of Jim McClarin, which is released in two parts :
Green-McClarin Filming study     Part One
Green-McClarin Filming Study    Part Two
For the record, where does the issue stand as of this date, October 3, 2011
1. I remain strongly convinced that a 25mm lens is not on the PGF camera, nor is there one on the Green/McClarin camera.
2. A 15mm specification may work for the PGF but will not work for the Green/McClarin filming, if Greenís camera position is proximate to his measured diagram.
3. A 20mm lens now seems to be a very credible and plausable option for both cameras, with the mis-alignment of the two lenses accounted for by different lens manufacturers.
4. The lens candidates currently considered more likely are a 20mm Kodak Anastigmat lens on the PGF camera, and a 20mm Comsat lens on the Green/McClarin camera. But this is simply the more likely candidate at this point of the new analysis, and should not be taken as a conclusion.
5. Lens distortion issues need further study and consideration since they impact on analysis of both the PGF and Green/McClarin footage. Render distortion in visualization software also needs to be studied further.
6. For photogrammetry software testing, I have concluded that the best results would be achieved if I rely on people extensively experienced in those software packages instead of my getting the software and trying to solve this matter as a novice user on a learning curve with the software. This is the primary reason I donít try to move forward with this at present. Such experts will require some compensation for their time and effort, and funding is not yet secured to do so.
7. A Bluff Creek Site visit is still a desirable thing to attempt, in hopes of collecting new data if the site can be truly verified (given it has changed to a point most people who visited it years ago canít even be certain they are in the same spot).
In closing, I need to acknowledge there seems to be a lot of enduring descriptions of this analysis which are not correct, and which I cannot change, despite my efforts to clear up the issue. All I can do is establish this website page which describes my work and current situation as best I can, and hope that people interested in the subject will be responsible enough to go to the source and read what I actually say, rather than rely on second or third hand descriptions of others about my analysis and its current status.