Welcome to 6picas! As this is the first post and this site is dedicated to learning everything about type, it only makes sense to start at the beginning. Thus we start out learning some of the basics of typeface anatomy…
The Em Square
Every character resides in an imaginary square called an Em Square. An Em Square is an imaginary square container that contains a coordinate system that directly correlates to the point size of the typeface (ie. If the typeface is set in 12pt then the em square will also be 12pt) The square is a direct descendant of the golden(or should I say lead) age of metal type. In metal type, each character sits on what is known as the body. All bodies must be the same height, from the capital M to the lowercase i in order to maintain straight lines. Looking at the metal type below, the individual letters all line up thanks to their body heights being the same.
Although there are differences in width (the metrics of individual characters in modern typefaces will be discussed later), highlighted by the blue boxes, the heights remain the same.
More Imaginary Lines?!
So every character resides in this imaginary square and within this square there are imaginary lines. Makes sense right? Well, first they aren’t necessarily imaginary, but they are invisible. Altogether these invisible lines make up what is known as the typeface’s metrics. A typeface’s metrics set the parameters such as the height of the capital letters, the lower case, and more. Let’s look at an example of a typeface’s metrics. Below is the word Typography in Adobe Garamond Pro Regular with visible lines representing where the typeface’s metrics(invisible lines) are.
Starting with the baseline, the baseline is the invisible line where all characters sit. Think of it as the blue line on ruled paper. Next we have the x-height. the x-height is named after the character height of the lowercase x. All lowercase letters are as tall as the x-height (sans overshoots, but that will be discussed later on) Another obvious name is the cap-height, which is the height of the uppercase letters in the given typeface. Finally we get to the ascender and the descender. The Ascender is the height of the lowercase letters that have a portion of their letter reaching above the cap-height such as: b,d,f,h,k, and l. The descender is the portion of the lowercase letters that extend below the baseline such as: g,j,p,q, and y.
So What’s the Point?
All Typefaces are based on an em square that contains metrics which are invisible lines that set the height of all the elements within a typeface.
em Square: An invisible square that contains the coordinate system for a given typeface and point size.
baseline: An invisible line where all characters reside.
x-height: the height of the lowercase x in a given typeface.
cap-height: the height of the capital x in a given typeface.
Descender: the portion of a letter that extends below the baseline.
Ascenders: the portion of a letter that extends above the cap height.