Glyph design: the lowercase b and l

o
i
a

b
l
n

d p q
e
f
v
h u m
r

c
j
t
y
w
x

k
z

g
s

     The letter 'l' is so easy to derive from the 'i' that I won't bother to cover it. You simply drop the tittle from the 'i' and extend the stem. A minority of designers think the top serif should be lengthened and the angle lessened though.

     The letter 'b' and its siblings 'p', 'd' and 'q' are derived from the 'o' and the 'l', but 'b' is substantially harder than 'l' to get right. The letter 'b' (or 'l', if you insist on going through that step) is also the first letter we make that has an ascender. An ascender is any stem or arc of stem of a letter than extends above the mean line (note that overshoots don't count as ascenders). Letters with ascenders are the ones that you would draw up to the solid blue line in kindergarten*, as opposed to the dashed blue line which crudely represented the mean line. Letters with ascenders include 'b', 'd', 'f', 'h', 'k', 'l', and arguably 't'. Inversely, a descender is a stem or arc of stem that extends down below the baseline, like in 'g', 'j', 'p', 'q', and 'y'.

     The proportion between the height of the mean line and the height of the ascender line is called the x-height, named because it's most easily measured from the letter 'x' and any letter with an ascender. In kids' handwriting books, the x-height is almost always 50 percent, but in most text typefaces, it's a little bit more than that. Smaller x-heights seem more quaint, while larger ones (up to the point of reason) are considered more readable.

Components of a lowercase 'b'

     Ascenders always have unilateral serifs pointing left, which in a non-didone typeface means that they are angled and pointy. Normally, serifs like that need an overshoot to look right, but since all the ascenders are like that, there are no flat tops to compare them to, so the overshoot is not a very meaningful concept here.

     In theory, the letter can be constructed by cutting off the left part of an 'o' and sticking it on an 'l', but this creates a pretty ugly looking 'b'.

A rudimentary 'b' can be made from an 'l' and an 'o', but substantial tweaking is needed.

     The most glaring problem is the serif on the bottom left corner of the 'b'. For whatever reason, a lowercase serif 'b' almost never has a serif sticking out of its bottom left (except for a few didones like Bodoni and Didot, and some computer serifs like Deja Vu). Some typefaces like Hoefler put a spur there instead of a serif, most link the bowl and stem with a simple corner.

Minion Pro and Proforma (left two) have a corner join, while Hoefler (right) has a spur. Garamond (third from left) has something of a hybrid join.

     The corner is also generally lower than the actual intersection of the 'o' and 'l'.

     But the bowl of the 'b' still doesn't quite look right. The bowl of the 'b' is much more elliptical than that of the 'o', and it's pushed in on the upper left and lower right. This is why you could say that the bowl has a second "outer axis" angled a little less than perpendicular to the actual axis. The upper join is also elongated and thinner.

     And a few last tweaks: