Legendecks Lab · calibration bench

Teach the scanner by showing it cards whose grade you already know

Photograph a slab, let Legendecks grade it blind, then enter what the grader actually said. Enough of those and the bias becomes visible and correctable — "we run six tenths high on corners" is a fact you can subtract, and it is the only honest route to a scan worth trusting.

Everything here stays in this browser. Nothing is sent to the Legendecks database, and no user's cards are involved — this is your own data about your own slabs, which is the whole reason it can be trusted.

What the bench has learned {{ biasN }}

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The correction, ready to apply

Paste this as the GRADE_OFFSETS variable on the legendecks-scan Worker. It is subtracted in code, so it is exact — the grader is not asked to apply it and cannot apply it twice.

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Why each number

Not correctable by an offset

Subtracting a near-zero mean would move every card without making any of them righter. These want sharper photographs or a tighter rubric, and that is work rather than a variable.

Left alone

Cloudflare → Workers & Pages → legendecks-scan → Settings → Variables and Secrets → add or edit GRADE_OFFSETS as a plain text variable, then Deploy. No code change, so recalibrating later is the same two minutes. Scan responses will report that a correction was applied and by how much.

The correction

Add a slab

Front photo — required

Choose front

Back photo — worth doing

Choose back

Shoot the slab flat, square-on, on a plain surface, with a margin of that surface showing all the way round. That margin is what lets the borders be measured rather than guessed.

What the grader said — the truth

Grader

Overall grade

Cert number

Sub-grades, if the label carries them. These are what make the bench useful per pillar rather than only overall.

Scan service

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NO
PHOTO

Legendecks

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Off by

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Import backup

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Nothing on the bench yet

Start with slabs you already own. Twenty tells you which way the scanner leans; forty or fifty lets you correct it with confidence. Cheap graded commons in the 6 to 8 range are worth buying deliberately — those are the grades that teach the boundaries, and a collection of 9s and 10s cannot.