Calibration board
SQUARE – mm
= – px
BOARD –

1 · Screen pixel density (from the spec sheet)

Enter the exact pixel density of this screen as the manufacturer states it (search “model ppi”, e.g. the Apple or Samsung tech specs). Do not estimate it: the board's size comes straight from this number.

Keep the browser zoom at 100 %. This page draws in whole physical pixels (device pixel ratio ).

2 · Verify the size with a bank card and a ruler

This does not change the calibration: it checks that the spec value above is right. Lay a bank card (85.60 × 53.98 mm) on the outlines, horizontally and vertically, and a ruler along the 100 mm block.

100 × 100 mm block

If the card does not match exactly: re-check the PPI in the spec sheet, the browser zoom, and the X / Y scale. Do not tune the PPI by eye.

3 · Board

The square is snapped to a whole number of screen pixels, so its exact size is:

–

Enter in Gnomon (Setup ▸ Calibration board): squares across, squares down and the exact square size above.

4 · Place the board

90° screen flat where the parts lie · board fills 80–90 % of the view camera fixed, straight down same distance as the parts
  1. Fix the camera on its stand, looking straight down. Set focus and exposure to manual in Gnomon (Setup ▸ Camera) and do not change them afterwards.
  2. Lay this device flat exactly where the parts will lie, screen up, full brightness, night-shift / blue-light filter off.
  3. Show the board full screen. It should fill most of the camera image (80–90 %).
  4. In Gnomon press Calibrate plane. For the lens (optional): hold the board in 10–20 positions and tilts across the whole image, Add view each time, Compute, then calibrate the plane again.
  5. Re-calibrate after changing the resolution, focus, zoom or camera position.

Tap the board to come back here. The screen stays on while the board is shown.