It's not just the scaling that can differ. Things that can be "user transparent" but different between formats and even imaging software:
- Image orientation (essentially the byte layout of the image)
- Overscan representation (how much and from what sides is overscan removed, or not)
- Scaling (do we represent 14 bits in 16 or scale 14 bits to 16? most scale FYI)
Probably other things as well but those are likely the big 3. Essentially for calibration to work and work well, you need to use the same format of data, taken with the same capture application. I doubt you'll find any 2 applications or formats that are compatible.
Thanks,
Jared