A clarification about kerning.

mauro sacchettomauro sacchetto Posts: 353
edited October 2020 in Font Technology
I take GaramondPremrPro for example.
The glyph of the / I / has: LB 35 and RB 26; the kerning added for the pair / II / is 9pt, so it is symmetrical: 35pt distance between the two serif close together at the bottom.
The glyph of the / E / has: LB 19 and RB 23. The pair / IE / has 9pt of kerning: in this case the two serif close together at the bottom are 54 pt apart.
The glyph of the / A / has: LB 4 and RB 1. The pair / AA / has 10pt of kerning, so that the two close serif below are only 15pt apart.
Are these different distances normal?
At least the couples / II / and / IE / shouldn't be equidistant?
Thank you


  • John HudsonJohn Hudson Posts: 2,869
    What matters is the optical space between the adjacent letters, not the distance between serif tips. Garamond Premier Pro is closely based on metal types, so has a lot more inconsistencies of serif length and shape than most digital types. If measuring, it is better to do so between the vertical stems of the letters—typically about halfway up the x-height—, rather than looking at sidebearing values.
  • mauro sacchettomauro sacchetto Posts: 353
    edited October 2020
    And what about fonts that don't have vertical stems, like / A / or / O /? Does everything play into what the eye suggests?
  • edited October 2020
    Start with numbers, then deviate by eye using smaller numbers.
  • John HudsonJohn Hudson Posts: 2,869
    Round shapes are complicated because unless they are perfectly symmetrical you can't rely on numbers, whether measured from the horizontal extrema or at a standard height. So a letter like O needs to be optically centred between uprights—HHOHH—and then the distance to other rounds checked—HOHOOHOH. That gives you the default spacing for caps against which other letters and kerning are checked. Diagonals complicate things because they produce so much additional white space; however, unlike rounds, it is often possible to use the same measurement on the left and right side taken from the stems at a standard height.

    In any font family, one of the first things I do is establish a standard height (usually about halfway up the x-height) at which I make all spacing measurements. This is key to being able to systematise spacing.
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