line-length-reading-flow
Compare the same paragraph under different measures while keeping text, typeface, size, and line-height fixed, so the effect of line length can be inspected without turning one measure into a universal optimum.
行長と読書リズム
line length / measure
Changing measure alone changes line-return frequency and horizontal eye travel, making different reading rhythms visible even when the underlying content and type settings remain constant.
Comparison
3 controlled conditions
narrow
Typography becomes easier to evaluate when the text, typeface, size, and leading stay fixed while only the measure changes. Short lines increase the number of returns, while long lines ask the eye to travel farther before finding the next line.
More frequent line returns and a visibly taller paragraph.
middle
Typography becomes easier to evaluate when the text, typeface, size, and leading stay fixed while only the measure changes. Short lines increase the number of returns, while long lines ask the eye to travel farther before finding the next line.
A comparison baseline, not a claim that this is the universally correct measure.
wide
Typography becomes easier to evaluate when the text, typeface, size, and leading stay fixed while only the measure changes. Short lines increase the number of returns, while long lines ask the eye to travel farther before finding the next line.
Fewer line returns and longer horizontal travel within each line.
Measure changes reading rhythm even when other typographic variables are held constant. The study intentionally does not establish one universally optimal line length; content, typeface, size, language, viewport, and reading context still matter.