Single-line vs. Paragraph Composers

Single-line composers—like the ones in QuarkXPress and Adobe PageMaker—only sets one line of type at a time, ignoring the lines above and below it. The result of this process is that, while many lines may look fine, some lines in a parargraph will be looser or tighter, giving an overall unevenness to the “color” of justified type.

InDesign includes a single-line composer, too, but it also has a “paragraph composer” which almost always sets better-looking type.