The difference in size you mention is significant, but typically there indeed is a safety margin for image resolution, called Kell factor [1] To examine "true"

The difference in size you mention is significant, but typically there indeed is a safety margin for image resolution, called Kell factor [1] To examine "true" resolution of an image one could look at its autocorrelation or Fourier spectrum [2] [1] https://en.wikipedia.org/wiki/Kell_factor https://en.wikipedia.org/wiki/Kell_factor [2] https://photo.stackexchange.com/questions/107911/how-to-determine-the-actual-or-true-resolution-of-a-digital-photograph https://photo.stackexchange.com/questions/107911/how-to-dete...