What do Butterick's Practical Typography pages say about line length, point size and colour that I can turn into checks for AI-made posters, title cards and thumbnails?

Problem. Generated layouts often have long lines, tiny type or loud coloured type on colour. Conditions. Butterick is body-text oriented (documents and web pages), so apply it to posters and title cards by analogy; thumbnails have very little text. Method (documented). Line length: aim for an average of 45 to 90 characters including spaces (or two to three alphabets per line). Point size: print body text 10 to 12 pt, web body 15 to 25 px; different fonts at the same point size do not necessarily look the same size, so judge by eye. Colour: contrast between light and dark draws the eye most; a thin or small font can carry a more intense colour than a heavy or large one; coloured type on a coloured background is usually regretted. Checks [inference]. (1) Count characters per line in any paragraph; credits and blurbs should sit within 45 to 90, and headlines of 1 to 6 words are exempt. (2) Compare cap or x-height of the type with its neighbours visually instead of trusting point-size names. (3) Limit to one emphasis colour, keep the lightness difference between type and ground large (confirm with P-L1-5-04 ratios). (4) For thumbnails, YouTube counts an impression only after the thumbnail is shown (C3-B578-01) and CTR comparisons depend on impression mix (C3-B573-03), so view the design at a small size before use and keep to a few big words [inference; no size numbers are taken from these sources]. Failure modes. Applying body-text rules to display typography mechanically. Limitations. Single-author book-website; opinions as well as rules. Version/date. Accessed 2026-10-23. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Promoted by C3R-0600 timed recheck: all cited excerpts re-located. Limitations: Author opinion with some rules of thumb; body-text focus. Mapping to thumbnails and title cards is inference. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

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      "url": "https://practicaltypography.com/line-length.html",
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      "note": "line length; point size; color; color; color; line length"
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      "url": "https://practicaltypography.com/color.html",
      "note": "line length; point size; color; color; color; line length"
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