I found only these notes in the SketchUp manual about pre-processing photos:
Do not crop photos. Match Photo currently requires that the point you aimed the camera at is located in the center of the image (also called the center of projection). Although it may seem possible to use a cropped image, typically vertical lines will not align well across a cropped image and the results will be unsatisfactory.
Do not warp photos. Images which have been manually warped using an image processing program, or specialized camera, are not supported by Match Photo.
Remove barrel distortion or issues where straight lines are bent away from the center of the image. Barrel distortion typically occurs on wide angle lens cameras. Use a third-party product to eliminate barrel distortion from images prior to using them within Match Photo. All cameras have a little bit of this distortion and it is typically worse around the edges of the image.
Point 1 is the most repeated advice about Match Photo.
Point 2, about warped photos, would seem to me to exclude using ShiftN. I can imagine using ShiftN to apply photo textures, but I presume its distortion of the photos will make them unsuitable for Match Photo.
Point 3 is what I assume Thomthom was referring to by "lens distortion". This lens appears to be excellent in that respect. It is extremely hard to find any evidence of barrel distortion.
But, as I reported earlier, I appear to have non-square pixels, the images as displayed are all a bit narrower than the model.
If anyone has any experience with how to accurately test that aspect of a camera lens, I would appreciate any suggestions. I will probably be working out my own tests this coming weekend.
I presume I will need a way to accurately identify the position of the center of the lens while the camera is on a tripod pointed at a flat surface that is exactly perpendicular to the camera's line of sight.
Theory is easy. Construction still awaits a design.
A brute-force approach would be to simply try different values for the adjustment until I find one that seems pretty good. But since it can take up to an hour of fussing and fiddling to reach what I consider my best compromise, that approach is guaranteed to take a few hours.
Again, brilliant ideas are always welcome.
Thanks,
August