OS/2 metric

mauro sacchettomauro sacchetto Posts: 251
edited May 2019 in Font Technology
About OS / 2 Metric: the fonts I have considered (Typo Ascent, Typo Descent, Line Gap etc) never coincide with those suggested by FontLab. Moreover the sum of Typo Ascent and Typo Descent should conventionally be equal to 1000 em for PS. Now, if these values ​​are not respected, what actually happens to the font?


  • Ray LarabieRay Larabie Posts: 972
    Not sure about IV but in FontLab Studio 5, avoid auto buttons in the Font Info menu except TrueType version record and Most important font dimensions. Supported codepages auto button can be helpful. Supported Unicode ranges auto button is useful but you need to uncheck ranges that have only minor support. For example, if you only have an Omega, it will count that as Greek range support.
  • Yes, I realized that many automatic functions do not give impeccable results (one for all: the StemSnap, which most often produces a very bad rendering). In any case, my question is rather about the role of metric parameters passed to OS / 2. Do they produce any actual font changes?
  • Frode HellandFrode Helland Posts: 143
    Messing with the Stem snap precision default settings is a bad idea in most circumstances. If you are instructing TrueType outlines manually, this setting can control when to round a distance up and when to round it down.
  • Yes, I found this, and in fact I reset the values ​​"by hand".

    But my thread was about something else, that is about the values ​​to pass to the OS / 2 metric, as I wrote in the first post ...
  • Frode HellandFrode Helland Posts: 143
    edited May 2019
    This is, IMO, the best introduction to understanding vertical font metrics. Your question is not easily answered, as it depends on a lot of variables.
  • Reading! The text says:
    And in order to avoid vertical jumping between different fonts of your family, it is a good idea to synchronise all values across all masters.
    If have I to syncronise the values in the various fields, is it all another matter the appeal to Family Blues and Other Family Blues?
  • Frode HellandFrode Helland Posts: 143
    edited May 2019
    Alignment zones and vertical metrics are not the same.
    Family Blues try to harmonize the rendering of a family of fonts, by making sure alignment zones with the same name round to the same height at the same size, even if they are slightly different (and would occasionally round to a different height) between the various styles.
    Vertical metrics determine the size of the invisible rectangle that the letters sit upon, and their vertical position within this rectangle. Those values should most likely be the same throughout a family of fonts.

  • Yes, I see... Now I'trying to make all metrics the same in all family fonts.
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