thorr said:
Yes, I was keeping the height constant on the PSB and only stretching the horizontal until the width and height matched the original aspect ratio. I also had to grow and shrink the original frame by dragging the corner so both dimensions would grow and shrink and keep the original aspect ratio. Eventually I got the original frame to the right height and then stretched the PSB until the width matched. It was kind of a pain. :-) Then when I overlaid the two, I pasted the new onto the old and then did undo, redo, undo, redo so I could flip back and forth to make sure it matched and that is when I noticed the PSB frame was very slightly crooked. The edges are straight so it is the frame inside that is crooked (definitely not a big deal).

Ok, that's a great method. So the horizontal stretching factor appears to be about 1.98. That matches the basic definition of 16mm scope being 2x.

It was more important to me to make the edges straight, so that when it comes time to crop, there won't be much image loss. By the way, it is not at all easy to get the frame straight with the workprinter.