Scale describes the ratio between an image and reality. At 1:1 a centimetre in the file is a centimetre in the fabric.
A photo has no scale of its own. It only gets one from an object of known size in the frame. In PatternScan Pro that is the four reference tiles, whose edge length is fixed.

Digitize sewing patterns without tracing.
Test PatternScan Pro free for 14 days with the full feature set. You need your smartphone, a printer and one pattern you always wanted digital.