Unless Jay has the originals he is forced to work with copies, or scans or reproductions and would be in the same boat as the pseudo-experts you keep bringing forth.
Not exactly. You are presuming what kind of case I would be making from the point of view of someone trained in photographic analysis and interpretation. I have specifically left that off, obviously because Robert is trying to bait me down that road in order to shift the burden of proof. And further, a discussion of the proper method of examination in this case (and indeed of all cases of questionable authenticity in an historical document) would involve the conventions and standards of proof that I alluded to earlier. Since I've asked Robert to say what those are and discuss them, I cannot really do so now without giving him the answers to questions I've asked him.
The portions of the backyard photo that Robert has posted here are extremely poor quality, and certainly not the best that exist. I have already shown in two ways how the quality of the photo would prohibit him from being able to conclusively state that the chin on the face in the photo cannot be Oswald's.
That is, I have shown two ways in which the condition of the data does not allow conclusive or deterministic extraction of 3D information from the photos that were posted, such that the true shape of the chin in the photo can be reconstructed from information contained solely in the photo. That may be possible from better copies of them, or from the original. We know that the originals, optical copies, or losslessly compressed digital copies would not suffer from the well-evidenced DCT boundary artifacts. But I'm skeptical that better copies would distinguish shade from shadow.
This is important. Robert's affirmative claim
relies on him being able to conclusively and deterministically extract accurate shape information from the photo. That is, he cannot affirm that it's not Oswald's actual chin without also claiming he can determine the shape of the depicted chin faithfully from the photo, preparatory to comparing it to an authentic reference.
There are known sources of error in such a determination. A defensible approach to producing a useful extraction requires attention to those errors and controls for them. Robert simply sidestepped them. Therefore he has no basis to claim that the difference in appearance of the chin
must be due to it being a different chin. He has not controlled for the other effects that might make the chin appear different.
Therefore the data we have in hand -- presuming they are the data that Robert has used -- are quite sufficient to determine that Robert's affirmative claim is unsupported. It is unsupported
precisely because the data are too poor to control for intervening variables, therefore the variable that is identified as the determiner of authenticity cannot be resolved.
Are the data in hand sufficient to rule out all claims that may be made? Hm, unknown. I haven't seen all the claims, and it's been a long time since I had a high-quality copy of the backyard image. I can say that the claims made
by Robert in this thread can be ruled out.