Frame size is the area of canopy captured per shot. At 1m distance a typical smartphone captures approx 1.2 x 0.9m. Calibrate once by photographing a tape measure across the canopy.

Reference object — hold a stick or rod of known length flat against the canopy face in every photo, with both ends clearly visible. High-contrast tape at each end (e.g. orange or pink) helps detection. Claude measures it in pixels to work out the true frame size for that photo.