What the camera sees · identical 4 mm discs on a 100×100 mm sheet
Measured too small
too large±10%
0° means the phone is exactly parallel to the sheet
0 = corrected main camera. Negative is barrel, positive is pincushion (assumed values)
1 mm at centre
One pixel
Coin long ÷ short axis
Disc size error range
Assumptions: a pinhole camera with 4032×3024 px and a 26 mm (35 mm-equivalent) lens. The camera aims at the centre of the sheet and tilts up/down. Disc size is the area-equivalent diameter. Model estimate from this series.