Kerning is the process of adding or subtracting space between specific pairs of characters. Tracking is the process of loosening or tightening a block of text.
Values for kerning and tracking affect Japanese text but normally these options are used to adjust the aki between roman characters.
You can automatically kern type using metrics kerning or optical kerning. Metrics kerning uses kern pairs, which are included with most fonts. Kern pairs contain information about the spacing of specific pairs of letters. Some of these are: LA, P., To, Tr, Ta, Tu, Te, Ty, Wa, WA, We, Wo, Ya, and Yo.
InDesign uses metrics kerning by default so that specific pairs are automatically kerned when you import or type text. To disable metrics kerning, select "0".
Optical kerning adjusts the spacing between adjacent characters based on their shapes. Some fonts include robust kern-pair specifications. However, when a font includes only minimal built-in kerning or none at all, or if you use two different typefaces or sizes in one or more words on a line, you may want to use the optical kerning option.
Optical kerning adjusts the spacing between adjacent characters based on their shapes, and is optimized for use with Roman glyphs. Some fonts include robust kern-pair specifications. However, when a font includes only minimal built-in kerning or none at all, or if you use two different typefaces or sizes in one or more words on a line, you may want to use the optical kerning option for the Roman text in your document.
You can also use manual kerning, which is ideal for adjusting the space between two letters. Tracking and manual kerning are cumulative, so you can first adjust individual pairs of letters, and then tighten or loosen a block of text without affecting the relative kerning of the letter pairs.
Word kerning isn’t the same as the Word Spacing option in the Justification dialog box; word kerning changes the kerning value only between a specific word’s first character and the word space preceding that character.
A. Original B. Kerning applied between “W” and “a” C. Tracking applied
You can apply kerning, tracking, or both to selected text. Tracking and kerning are both measured in 1/1000 em, a unit of measure that is relative to the current type size. In a 6‑point font, 1 em equals 6 points; in a 10‑point font, 1 em equals 10 points. Kerning and tracking are strictly proportional to the current type size.
Tracking and manual kerning are cumulative, so you can first adjust individual pairs of letters, and then tighten or loosen a block of text without affecting the relative kerning of the letter pairs.
When you click to place the insertion point between two letters, InDesign displays kerning values in the Character panel and the Control panel. Metrics and optical kerning values (or defined kern pairs) appear in parentheses. Similarly, if you select a word or a range of text, InDesign displays the tracking values in the Character panel and Control panel.
You apply either of two types of automatic kerning: metrics kerning or optical kerning, or you can adjust the spacing between letters manually.
If Metrics is applied to fonts (including some Japanese OpenType fonts) which do not contain pair kerning information, spacing for each character will be set to “0” and character compression will not occur.
To avoid using the built-in kerning information of a font for selected text, choose “0” in the Kerning menu.
The default setting is Metrics – Roman Only. When Metrics - Roman Only is applied to Roman OpenType fonts, kerning is the same as when Metrics is selected. When Metrics - Roman Only is applied to CJK OpenType fonts, only the Roman characters will be kerned with kerning pairs as if Metrics were set. The CJK characters will not be kerned, as if '0' were set. For this reason, choose '0' to turn off pair kerning.
If you use font metrics kerning in a Japanese OpenType font, it is recommended that you choose OpenType > Use Proportional Metrics from the Control panel menu. That way, you can avoid making unnecessary manual kerning adjustments.
Optical Kerning is designed on the basis of Roman character forms. You can use this feature with CJK fonts, but you should always check the results of the operation.
If a range of text is selected, you can’t manually kern the text (you can choose only Metrics, Optical, or 0). Instead, use tracking.
If a range of text is selected, you can’t manually kern the text (you can choose only Metrics, Metrics - Roman Only, Optical, or 0). Instead, use tracking.
The amount of the word kerning adjustment is the same as the Kerning value in the Units & Increments Preferences dialog box. When you press the shortcut and hold down the Ctrl or Command key, the kerning amount is the Kerning preferences value multiplied by 5.
You can also press Alt+Ctrl+Q (Windows) or Option+Command+Q (Mac OS) to reset kerning and tracking. When you do so, kerning is set to Metrics regardless of which kerning option was previously applied.
In some instances, you’ll want to be aware of text that has custom tracking and kerning applied. If you select the Custom Tracking/Kerning preferences option, green highlighting appears over text with custom tracking or kerning.