Calibration scale

Print this page at 100% — no "fit to page", no scaling. The bar below is then ten millimetres, edge to edge. Photograph it through your clip lens, then tap its two ends in the app.

012345678910 mm

Each division is one millimetre. Total length: 10 mm.

How to use it

  1. Print, and check the bar with a ruler — if 10 mm reads 10 mm, the page is right.
  2. Clip the lens on the phone, lay the phone face-down over the bar so the lens sits over the 0 mark.
  3. In the app, press Calibrate, then tap the two ends of the bar on the picture.
  4. The app now shows µm per pixel. Any measurement after that is in microns.

If the lens moves, recalibrate. Tape, pocket lint or a phone case that shifts the lens by a millimetre changes the scale, and every number with it. Re-check the calibration whenever the setup changes, and at the start of each session.

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