A card's centering is measured using a ratio to represent the percentage of border on either side of the card. A card is considered "perfectly-centered," or "50/50," when the distance between the photo and the edge, is the same on opposing sides of the card. As the one number increases and the other number decreases, the centering begins to deteriorate. A card's centering will be measured twice; left-to-right and top-to-bottom.

Let's say you have a card, and you wish to find it's centering. You measure that the distance from the left edge of the card to the left side of the photo is 3mm, and from the right edge to the photo is 2mm. Since the measurment from the left edge of the card to the photo, is greater (by a ratio of 3:2), the card's left-to-right centering would be "60/40."

See Also: Miscut, and Diamond Cut.