Centering in TCG Grading — How Border Symmetry Is Measured
Centering is the ratio of border width on opposite sides of a trading card's printed image, expressed as a percentage pair like 55/45 (left/right) or 60/40 (top/bottom). PSA accepts 55/45 or better on the front for Gem Mint 10; BGS requires 50/50 for Pristine 10. Centering is a print-time defect — it cannot be improved post-production.
Detailed explanation
Centering is measured by comparing the width of the outer border on opposite sides of the printed image, then expressing the imbalance as a percentage ratio. A perfectly centered card is 50/50; a card where the left border is 40% wider than the right is 60/40. Grading houses publish thresholds: PSA accepts 55/45 front / 75/25 back for a 10; BGS requires 50/50 / 55/45 front / back for Pristine 10; CGC publishes similar tolerances with slightly different math.
Centering is the single most common reason a modern card with otherwise mint surface and corners fails to hit Gem Mint. It is a manufacturing defect — set at the cutting die, baked in before the card ever reaches a player. Some sets (1999 Pokémon Base Set, modern Yu-Gi-Oh Ghost Rares) are notorious for centering variance.
Common misconception: centering means the artwork looks centered to the naked eye. It does not — it is a ratio of the printed border, not the artwork inside it. A card whose art looks lopsided can still score 50/50 if the border itself is symmetric.
How AuraGrade measures it
AuraGrade's pipeline rectifies the card to a frontal plane using detected corners, then uses LAB color-space chroma channels to locate the inner art window's edge against the outer border. We compute left/right and top/bottom ratios from pixel counts, which works across Pokémon yellow, MTG black, and Yu-Gi-Oh dark borders without per-set calibration.
Worked example
A 1999 Pokémon Base Set Charizard with left border 220 pixels and right border 180 pixels yields 220 / (220+180) = 55%, ratio 55/45 — pass for PSA 10. The same card at 240/160 yields 60/40, triggering PSA's MC qualifier and capping the grade at PSA 9 regardless of corners and surface.