Readable letter size cannot compensate for a caption that disappears before a viewer can finish it. Compare text quantity with actual display duration, then review the cue in context. A line can fit neatly on the screen and still carry too much information for its time. Layout, reading load and meaning need separate checks.
Calculate a diagnostic reading load
Record each cue's start, end and visible text. Divide a consistently counted character total by the display duration to make a comparison measure. State whether your method counts spaces and punctuation. Different conventions and languages can change the result, so the arithmetic is a diagnostic tool rather than a universal readability guarantee.
Watch the cue at normal playback speed without pausing. Note whether the viewer must also inspect a diagram, follow an action or recognize a new name. Equal character rates do not imply equal difficulty when the information or visual task differs.
Use the receiving specification narrowly
Netflix's English USA guide includes reading-speed requirements for its own subtitle deliveries. Those limits are not universal presets for Chinese captions, every age group or every social platform. Use the actual receiving contract and count convention when compliance is required.
Revise a crowded cue by considering segmentation, available timing and carefully reviewed text. Do not stretch it into the next speaker's line or reveal an answer before it is spoken. If reducing words, preserve names, negation and the verified claim. A smaller font can make both size and reading-time problems worse.
A hypothetical two-duration comparison
Suppose a test cue contains sixty characters under a stated counting method. At two seconds it has a calculated load of thirty characters per second; at four seconds it has fifteen. Those are arithmetic results for this invented cue, not proof that either version is approved for a destination.
Compare two candidates with the same verified meaning and watch the action. The longer one may be easier to read but may overlap the next answer. Record cue duration, count method, observed reading completion and speech relationship. This is a proposed test, not a measured audience result.
Approve reading and synchronization together
Accept when representative viewers can read the required information while following the scene and the timing reflects the actual speech or intended text event. Reject an early spoiler, missed qualification or a layout that passes a numerical limit while obscuring the important action. Review the densest cue as well as an ordinary one.
Keep the transcript, timing revision and final subtitle file. Recheck reading load after translation or recutting because the text and available time can change independently. Imagild's Skills can develop visuals, while subtitle timing and delivery are handled in the selected external editor. A useful review records both what the arithmetic says and what the viewer can understand.