Questions on Height Dimensions

SIL Fonts
1

Greetings,

I’m trying to get up to speed with design principles and best practices for setting vertical dimensions in fonts. There are often discrepancies between what I read in OpenType documentation and guides, and what I see in practice that I’d like to understand -I assume it is the experience of the type designer that is seen here.

In Abyssinica SIL, the height points of the Latin letters are consistently at 1374 points, however, the Caps Height is set to 1108 -shouldn’t these be exactly the same? Why would they be different?

I see this difference in many fonts which has me wondering how seriously to take the Caps Height and x height dimensions. In a multi-script font, does the Caps Height and x height impact the non-Latin letters in any way when the fonts are used by applications?

What approach is taken to set the height of the non-Latin letters relative to the Latin letters? “H” is often used as a reference letter, is a reference letter selected from the non-Latin script and then sized against “H”? Or against the Caps Height?

This is my untrained instinct, I’m often surprised though to find fonts with Latin letters paired with non-Latin letters with surprisingly different heights relative to one another, so there seems to be another design principle at play here.

thanks!

-Daniel

2

Hi Daniel,

Vertical sizing and metrics is rather complex. Caps height and xheight are virtually ignored - think of them as loose guidelines for the designer. Balancing the height/size of Latins with other scripts is very script-specific, and should be set based on what people would most commonly expect. It is usually the case that Latin caps and/or ascenders are at a different height then the letters of other scripts.

For more detailed strategies see these two articles:

Design Metrics
Line Metrics

1 Like
3

In the original post a question was how high should the non-Latin letters be compared to the Latin letters. In some font projects, this question is reversed, the non-Latin letters are drawn first, and the Latin scaled to match it. In addition to height, the weight of the glyphs needs to be considered. For example, if I want to use Gentium Plus for the Latin part of a non-Latin font, would I choose Gentium Plus or Gentium Book Plus (heavier than Gentium Plus). A good test for mixed script fonts would be to set a whole paragraph of text, alternating between the scripts, and see what looks good (so that one script does not stand out too much from the other script). Printing out that test and seeing the paper from different angles would also be helpful.