Is a 1500 upm ok?

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ok_locksmith_8414
ok_locksmith_8414 Posts: 3
in Type Design Technique & Theory

Ok so long story short, I’ve posted here before about a typeface I’m designing. The typeface has a units per em value of 1500. I know some of you might say that the most common values are 1000 and 2048.

When I first started working on this project, I was still very new to using Glyphs App and thought that changing the units per em was a way to scale the glyphs up which is what I wanted to do at the time. That was about 1 year ago, and I hadn’t really thought about it again until recently, when I heard that typefaces can run into issues in some environments if they don’t use 1000 or 2048 units per em.

However, I hear with modern technology, using values other than 1000 or 2048 isn’t necessarily a problem. The good news is that my typeface interpolates wonderfully at 1500, and the sizing looks fine when I test it alongside other fonts like Inter and Helvetica.

I really don’t want to go through the hassle of scaling everything down, fixing errors, and learning new metrics. Should I just leave it at 1500 and hope for the best?

Best Answers

  • Thomas Phinney
    Thomas Phinney Posts: 3,024
    Answer ✓
    Yes

    For most purposes, that is absolutely fine. You can use any em value between, roughly 700 and 2500 and everything is fine. Maybe even 3000 or so.

    There are a few players who might care (e.g. Microsoft) so different rules apply if you are making a font specifically for them. But generally, it is a non-issue in the real world today.
  • John Hudson
    John Hudson Posts: 3,439
    edited July 10 Answer ✓
    Back in 2008, when work first began on the Brill types, there was a known issue with some third party PDF tools and viewers incorrectly assuming that all CFF-flavour OpenType fonts would have a 1000 UPM, resulting in incorrect scaling and/or linespacing. That no longer seems to be an issue, so for v5.00 we scaled everything up to a 4000 UPM to enable easier handling of fine details.

Answers

  • Matthew Smith
    Matthew Smith Posts: 98
    I can’t speak to the technical limitations of how high you can go, but if it means anything to you, Sharp Type’s Carta Nueva has a UPM of 4096.
  • Thomas Phinney
    Thomas Phinney Posts: 3,024
    There have been some historical issues, one of which John mentions. But as far as I know, they have been long since resolved.

    Google’s icon fonts have a non-standard em square, as well. Material Symbols have a 960-unit em square (with TrueType outlines, not CFF), and their predecessor Material Icons had a 480-unit em. I did end up doubling the em square when developing Material Symbols (which started in 2020), but only late in the game, and purely for design reasons — not because of bug reports with either the new font or its predecessor.
  • Igor Petrovic
    Igor Petrovic Posts: 324
    I follow 1000UPM wherever it is possible, because all reference numbers in a font (overshoot, stem thickness in thin and black master, etc.) are usually presented at that resolution (in my head and in other typefaces).

    For example, I know that the lowercase vertical stem in the black master is usually somewhere around 200 units. In thin ~25 units. And gives me a general direction I like to have.

    If a font requires more detailed resolution because of its design, then I go to 2000UPM because it is easier for me to count reference numbers that way. Also, it is usually quite sufficient in a technical sense.

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