Calibration paper
A photo on its own cannot tell how big a piece is, what colour the light was, or how much the lens curved the picture. The calibration paper answers all three: you print it, lay your item on it, and the AI measures against what is printed around it.
It does not make an estimate certain. It takes away guesses a photo would otherwise force: the size, and with it the weight estimate, rests on something measured, and the colour is judged against patches whose colour is known.
Print in colour at 100% — never “fit to page”. Both files carry the same zones at the same size; pick the paper your printer takes.
What is on the sheet
Checker border
Five-millimetre squares around the zone. They give a known size, and because they are printed straight, they show how much the phone’s lens bends the picture.
Corner codes
Four square codes that mark the corners of the zone and which way up it lies, so it can be found even in a tilted photo.
Colour chart
Twenty-four patches of known colour. The AI can judge the light against them, so a warm lamp is less likely to make white gold look yellow.
Focus star
A star of fine black and white wedges. It shows at a glance whether the shot is sharp or soft.
How to use it
Print it in colour at 100%
Use plain, matte white paper. In the print dialog, turn off “fit to page”, “shrink to fit” and any other scaling — they change the size and the sheet is no longer a reference.
Lay it flat and place your item
Soft, even daylight works best. Put the item in the middle of the zone that fits it, inside the corner marks, without covering the border or the chart.
Choose “Calibration paper” in the app
When the app asks which reference object you used, pick Calibration paper. Keep the whole zone, border included, in the first shot.
Which zone for which item
Zone S
70 × 95 mmItems up to 40 mm across
Rings, earrings, coins and small pendants.
Zone M
110 × 150 mmItems up to 85 mm across
Bracelets, watches and larger pendants. Coil a chain loosely inside it.
Bigger than 85 mm? Lay a bank card beside it instead — the paper is built for pieces that fit inside a zone.
Check the print
The bank-card outline. Lay any bank card on the outline at the bottom of the sheet. It should cover it exactly, 85.60 × 53.98 mm.
The 180 mm scale. No card to hand? Hold a ruler against the scale along the bottom edge. It must measure exactly 180 mm.
If either is off, the print dialog scaled the page. Set it to “actual size” or 100%, turn off “fit to page”, and print again. A sheet that is even a few percent out makes every size reading wrong by the same amount.
No printer?
A bank card or a coin still works. Lay it beside the item in the first shot and tell the app which one you used. It gives the AI a size to measure against — just not the colour chart or the grid.
Back to how a scan works