Calibration Card
The calibration card gives the tool a known reference size so it can estimate your grind. Print one at home for free, or order a durable pre-printed card.
Print at Home
No cutting required. Print the full sheet on plain white paper, spread your grounds inside the marked zone, and photograph. The quickest way to get started.
Prefer a wallet-sized version? You can also and glue it back-to-back.
Pre-Printed Pocket Card
A durable, wallet-sized card printed and shipped by Shot In The Dark — accurate, reusable, and always ready at your coffee station. Rs. 800 inclusive of taxes, delivered to you.
Interested? This opens a ready-to-send email to [email protected] — just add your name, phone, and delivery address, and send.
How to Set Up
Step 1: Get Your Card
Download the free print-at-home card below, or order a durable pre-printed card delivered to you.
Step 2: Print at 100% Scale
Use any white paper and set scale to 100% (no fit-to-page). No cutting needed — just print and go. Check the 10mm scale bar with a ruler to confirm the size.
Step 3: Scan Side Up
Place the card scan-side up (the white side with 4 corner markers). On the pre-printed card, the branding is on the other side.
Step 4: Spread & Photograph
Spread a thin, even layer of coffee grounds on the white area. Photograph from directly above with all four corner markers visible.
Photography Tips
Use good, even lighting — natural daylight works best
Spread grounds thinly so individual particles are visible
Keep the camera perpendicular to the card (directly above)
Include all four corner markers in the frame
Avoid shadows across the card — they interfere with detection
Don't pile grounds too thick — overlapping particles can't be measured
Don't cover the corner markers — they're needed for calibration
Understanding the Card
Corner Markers
Four calibration markers sit at the corners, a fixed distance from the edges. The tool uses these to work out the exact scale of your photo (how many pixels equal one millimetre) and to detect which card you're using — so it always measures against a known size.
Auto Card Detection
The tool automatically recognises whether you're using the print-at-home sheet or the wallet-sized pre-printed card, and adjusts its measurements accordingly. There's nothing to set up — just photograph and analyse.
White Measurement Zone
The entire scan face is the measurement zone — a bright white area where you place coffee grounds. The white background provides maximum contrast against dark particles, allowing accurate segmentation and measurement of individual grains.
Scale Bars
5mm and 10mm reference bars on the printable card let you verify it was printed at the correct size. Measure with a ruler — the 10mm bar should be exactly 10mm.