In digital typography, kerning refers to increasing or decreasing the distance between two adjoining characters (or between a character and an adjoining space). (It can also refer to adjusting the space between various letter combinations in a digital font.) Tracking refers to uniformly increasing or decreasing the letterspacing over a whole string of characters (or for all characters set in a given paragraph or character style defined with InDesign’s styles feature).
    (“Kerning,” in hand typesetting, meant something different. It was done by the typefoundry at the manufacturing stage, or in the shop with a specialized mortising machine, and it was not done casually.)

To adjust kerning or tracking in InDesign, place the cursor where you want to add or take out space, or select the string of characters you want to adjust. (To set tracking for a style, specify the track numerically when setting up the style.) With the cursor placed or the string selected, hit the kerning/tracking keyboard shortcut, which is Option-Left Arrow to decrease kerning/tracking, and Option-Right Arrow to increase it.

In order to work successfully and efficiently with kerning and tracking in InDesign, you need to change the magnitude of the adjustment made when you hit this keyboard shortcut. In InDesign’s Preferences menu, go to the Units and Increments preferences. At the bottom of the panel, under Keyboard Increments, set the Kerning/Tracking increment to 5/1000ths of an em. (The default is 20/1000ths, which is much too coarse. It was one of the very first things I changed when I first set up InDesign at home.) With this setting, every time you hit the keyboard shortcut, kerning/tracking is adjusted by 5/1000ths (=1/200th) of an em.

(For more about “units” in kerning and tracking, see the article “Units”: A Fundamental Measure of Space And Width.)

I have learned from long experience that 1/200th of an em is, with rare exceptions, the smallest useful increment for kerning or tracking. It is also a commonly useful increment by itself: most adjustments you make will require that you hit the keystroke from one to three times.
    1/200th of an em was the default increment in Quark. It was one of the few defaults that Quark got right. (Quark’s bad defaults were one reason why InDesign knocked Quark out of the market so quickly.) Unfortunately, InDesign’s 4/200ths (20/1000ths) was one of the few defaults Adobe got wrong. This may be why the great majority of InDesign users, who don’t know about preferences and how to change them, don’t think in terms of manual kerning.
    In 10-point type, 1/200th of an em is 1/20th of a point. That may seem insanely fine, but if you experiment, experience will soon confirm that it is the unit you need to work with. In order to minimize the legibility tradeoffs when you add or decrease letterspacing, kerning and tracking adjustments must be as fine as is practically possible. Note that when adjusting tracking, the increment is multiplied by the number of letters in the string you are tracking, so tiny adjustments add up to big ones.

If you are going to take full control of kerning, tracking, and text aesthetics in InDesign, there is another important departure to keep in mind. You will, of course, be setting up your document using paragraph styles. In the Paragraph Style Options for each style, click Justification in the sidebar menu. In the Composer setting, at the bottom of the resulting panel, be sure that Adobe Single-Line Composer is selected. The other choice, Paragraph Composer, tends to override manual adjustments you may make, while its own performance in balancing tradeoffs, though creditable, is not always equal to that of a skilled typographer. The Paragraph Composer, if I recall correctly, is the InDesign default. (Bringhurst, ignoring the possibility of fine-tuning, tells you to rely on the Paragraph Composer.)

InDesign’s achievements in automating good text aesthetics are impressive, but it is a mistake to consider them as beyond improvement. That some may think of InDesign as the final word on the matter is perhaps a consequence of the contrast between the InDesign’s good-to-excellent default performance and the awfulness of the justified text produced by InDesign’s predecessor, Quark, in its default configuration.
    (Not one designer in a thousand knew enough to change Quark’s default configuration, though it could be done in seconds by changing a few numbers in the Hyphenate-and-Justify preferences. The many designers who bloviated endlessly about typographic aesthetics, and the empowerment they gained from new technology, never knew those preferences existed, let alone what the right numbers were.)

The process of making local adjustments to kerning and tracking in InDesign (or Quark) is very much like the process of adjusting letterspacing in hand-set type—except that it’s incomparably faster, easier, and more effective, so there’s even less excuse for ignoring it in digital typesetting. I hope to be writing about the details of this process in the future.

BRUCE ROGERS ON TEXT AESTHETICS IN BOOK PAGES

(p. 50) “The evenness of spacing that the early printers got came from their abundant use of Latin abbreviations [and alternate spellings—kd] and their indifference as to how many consecutive word divisions occurred at the ends of lines, but it was never a conscious effort to obtain what is called ‘texture’ in the page. There should be no laboring to produce a perfectly spaced page but rather an endeavor to avoid a badly spaced one.
    “Don’t try to ‘design’ every page of type throughout a book, or work it over too carefully after the style is chosen; leave something to accident, so long as it is not a glaring defect.”

(p. 56) “It is ... a mistaken ideal to try to make all lines fill the full measure, so as to produce a solid rectangle of type. One doesn’t mind a solid rectangle occasionally, when it comes naturally so, but too much of it is monotonous. Many designers attack the problem as though they were engineers rather than artists. Monotony of effect should be avoided rather than striven for.”

(p. 58) “It is sometimes unavoidable to make facing pages either long or short to take care of “widow” lines; but every effort should be made to avoid them if the make-up can be rearranged without too much overrunning in order to gain or lose lines. It seems a little too finicky to demand consistent uniformity in length of page throughout a book, especially when some pages may run short for textual reasons.”