Font Metrics & Point Size

Matt Khinda

Hey,

Here's a potentially silly question I have for you all...

In one of the typefaces I'm working on, I realized that the same point size is by default bigger than (almost) every other typeface I compared it to. I know x-height, ascenders and descenders can affect this, but I'm put off by the fact that none of the other cap-heights are as tall as mine.

Am I using weird or incorrect metrics? Is this an issue or just a design difference?

(image for reference, all typefaces set to 30pt Bold) 

Thanks!

André G. Isaak

If you're unhappy with it, one way to reduce the size of your design without compromising quality or doing actual work would be to simply increase the font's UPM size by 10% or so.

Matthew Smith

You may find this page on Font Forge helpful:
http://designwithfontforge.com/en-US/The_EM_Square.html

In short, the rendered type size is determined by the relationship of the metrics of the design to the UPM you're using. Commonly, fonts are built with 1000 UPM (1000 units per em), and when they are typeset they are scaled to the point size. 

Fonts vary in sizes because it all depends on how the designer chose to approach their work. How big or small your font looks depends on how large or small you've made your design within your UPM.

If you're designing a font with 1000 UPM, and the cap height is at 700 units, the cap height will render at 7pt when typeset at 10pt.

Often times new type designers make their metrics larger than necessary because they haven't yet considered diacritics. This isn't always the case, but it easy to overlook when you're first getting into things. If you want to ensure that your diacritics don't get clipped (across browsers and software) then you may need to size down your design within your UPM.

Script faces with big flourishes also tend to have really tiny x-heights because they follow a similar approach of trying to avoid any clipping from happening.

I hope that's helpful!

Thomas Phinney

Matthew Smith said:

Often times new type designers make their metrics larger than necessary because they haven't yet considered diacritics. This isn't always the case, but it easy to overlook when you're first getting into things. If you want to ensure that your diacritics don't get clipped (across browsers and software) then you may need to size down your design within your UPM.

This! It was the first thing I thought of when I saw your cap height (and secondarily, your x-height.

A typical cap height is 65-72% of the em. 70% is about average.

Matt Khinda

Often times new type designers make their metrics larger than necessary because they haven't yet considered diacritics. 

Well this sounds pretty dead on. Thanks for the insight! 

In the interest of "doing things the right way" what would be best practice for adjusting?

Reducing the metrics (by about 30% following @Thomas Phinney's rule of thumb) and then scaling the existing letterforms down using a transformation?

André G. Isaak

If you scale down, you face the risk of quality-loss due to rounding errors. Increasing the UPM size will effectively reduce the size of the glyphs on the em-square without actually changing any of your design coordinates and thus eliminate the need for clean-up afterwards.

Mark Simonson

Most font editors have an option to scale everything in the font when you change UPM. The easiest way to reduce the size of your font is to change your UPM from 1000 to something larger, but with the scaling option off. This will have the effect of reducing the size of your outlines relative to the UPM without changing anything else. If you want the UPM to be 1000, turn the scaling option on and change it back to 1000. (André's warning about rounding errors applies.)

John Savard

Matt Khinda said:

In one of the typefaces I'm working on, I realized that the same point size is by default bigger than (almost) every other typeface I compared it to. I know x-height, ascenders and descenders can affect this, but I'm put off by the fact that none of the other cap-heights are as tall as mine.

I remember back in the early days of computer laser printers noticing that "10 point Times Roman" was smaller on a laser printer than it used to be in hot metal.

So, from my point of view, it's possible that you're not the one doing something wrong. I suspect the reason for this is so that it is easier to mix different typefaces without having to think about it: when printing type was simplified to make it easier for printers to align different typefaces, there were still three different positions the baseline could take on the typeslug: near the bottom for "Titling", about 1/5 of the way up for "Standard Line", and about 1/3 of the way up for "Script Line".

So that people can just use any typeface in a word processor, I suspect that there is only one baseline for computer typefaces normally used. So they shrank the letters to make them all fit.