Multilingual Typesetting Note: Optimal line spacing varies by language

What do you think of this typesetting?

This typesetting is difficult to read and the content is hard to understand, so I would like to make some modifications. Where and how should I make the modifications?

Negative Points

Improvement Plan

English reduces the line spacing compared to Japanese

Line spacing greatly affects the readability of a text. Just like character and word spacing, there is a balance between too wide and too narrow line spacing, but this example is too wide. When line spacing is too wide, it can appear scattered and make it difficult to gather thoughts for the next line. It can also resemble a textbook (with wide spacing for note-taking), which is not suitable for the purpose of engaging native readers.

On the other hand, if the line spacing is too narrow, it is not good. It can be difficult to understand which line you are reading, and you may get lost when moving to the next line or end up reading the same line again. It is unacceptable for the characters to collide with each other vertically.

For standard English fonts, it is recommended to adjust the line spacing starting at around 120% of the font size. If you are unsure, it is recommended to make it narrower. Japanese people tend to unconsciously use wider line spacing.

The optimal line spacing is influenced by conditions such as font and line width, so it is not feasible to determine it uniformly, such as "○○ font is 10pt/12pt". When the line width is narrow, such as in a newspaper, the amount of eye movement decreases, so line spacing is not as necessary. On the other hand, when the line width is wide, increasing the line spacing makes it easier to avoid losing track of where one is reading.

Have you ever had the experience of not being able to understand the content of a seemingly simple sentence? It could be due to issues with typesetting, such as incorrect spacing between lines, words, or characters, rather than the individual's comprehension or focus.

The default value for InDesign's automatic line feed varies depending on the language, with a significant difference between the Japanese version at 175% and the English version at 120%. In many cases, if Japanese data is used for English text, the layout becomes too wide. When converting from Japanese to English, be sure to narrow the line feed. Even when using both Japanese and English, the line feed should not be aligned, and the line feed for English should be adjusted to be easy to read as English.

When expanding to multiple languages

English with many diacritical marks (auxiliary symbols)

If you are dealing with Eastern European languages or Vietnamese, which have many diacritical marks, it is recommended to adjust the spacing slightly wider than English to avoid feeling cramped.

Arabic characters

Pink highlights indicate areas where Arabic characters may extend beyond the top and bottom of lowercase Latin characters. Arabic characters are typically taller than Latin characters, so they may need to be widened to avoid overlapping with the characters above and below. Some fonts may also have misaligned baselines or unbalanced sizes between Arabic and Latin characters, which may require additional adjustments.

Thai characters

Thai characters have tall letters and stacked pronunciation symbols, so it is better to leave some space between lines. Depending on the font, the character size may be noticeably smaller than Latin characters with the same point size, so overall adjustments may be necessary.

Blank Hierarchy

The spacing on typesetting is as follows: letter spacing

If you have a good body font, you don't need to make any special adjustments to the letter and word spacing. The line spacing is up to the typesetter's judgment, but the optimal line spacing will vary depending on the language, layout, and font, so let's decide each time. It is unreasonable to simply align the line spacing to Japanese or English without much thought.

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Main Reference Materials

Jost Hochuli, Detail in typography, Éditions B42, 2015
Cyrus Highsmith, "The Basics of European Typography", Graphic-sha, 2014
Masao Takaoka, "Revised and Expanded Edition: Fundamentals and Etiquette of European Typesetting Typography", Uyushorin, 2019