Graphics Reference
In-Depth Information
This line is set with plus ten units of interletter spacing.
This line is set with normal, unaltered interletter spacing.
This line is set with minus five units of interletter spacing.
This line is set with minus ten units of interletter spacing.
This line is set with minus twenty units of interletter spacing.
Univers
53 em
55 em
57 em
59 em
2-40
2-42
For design considerations, the em of
a condensed typestyle can be narrower
than a square, and the em of an expanded
typestyle can be wider than a square. This
is demonstrated by the em quads from four
styles in the Univers family of typefaces
(Fig.
2-40
).
While
em
and
en
are still used as
typographic terms, spacing in digital
typesetting uses a unit system. The
unit
is a relative measurement determined by
dividing the em (that is, the square of the type
size) into equal vertical divisions. Different
typesetting systems use different numbers of
units; 16, 32, and 64 are common. Desktop
publishing software permits adjustments in
thousandths of an em. The width of each
character (Fig.
2-41
) is measured by its
unit value.
During typesetting, the character is
generated, then the software advances the
number of units assigned to that character
before generating the next character. The
unit value includes space on each side of the
letter for normal interletter spacing. Adding
or subtracting units to expand or contract
the space between letters is called
tracking
.
Changing the tracking changes the tone of the
typography (Fig.
2-42
). Tracking influences
the aesthetics and legibility of typesetting.
Some letter combinations, such as
TA
,
have awkward spatial relationships. An
adjustment in the interletter space to make
the interval more consistent with other letter
combinations is called
kerning
. In metal type,
kerning was achieved by sawing notches in
the type blocks. Contemporary typesetting
software contains automatic kerning pairs,
and the designer can manually change the
kerning between characters when these
awkward combinations appear.
The unit value of each letter in the word
Design
is shown.
In this setting, minus one unit is used for tighter interletter spacing.
In this setting, minus two units is used. The letters touch.
2-41
