How much detail an icon carries sets how small it can go
Aliases: detail density · shrink floor · stroke collapse
What it is
How small an icon may go is answered first by how many parts must remain separately visible: gaps, junctions, teeth, holes. When the part count exceeds what that pixel budget can feed, junctions fuse, holes fill, teeth become frayed. The floor is not a universal minimum edge. It is a reconciliation between this drawing's detail density and the pixels on offer. Denser drawings hit the floor sooner.
Why it happens
Strokes have width. Once the gap between two strokes falls below about one stroke, they first merge into a fatter line and then into a blot. Interior counters likewise need a ring of pixels to stand; a hole too small to hold a pixel is rounded away. High detail density means more strokes and more holes to keep alive inside the same edge length, so the books fail earlier. Subject matter is irrelevant: a toothed key is not "more important" than an arrow; it merely asks for extra slits at 16 px. After the melt, the visual system still registers a blob, but no longer what it is.
Studying it
Draw several levels of the same subject with a countable part list (junctions, holes, independent strokes) and run naming or matching across a fixed sequence of edge lengths. Independents: detail level and edge length. Dependent: the edge at which identification drops — that drawing's floor. Counting still-separate gaps on the pixel grid estimates a physical floor, then behaviour calibrates it. Anti-aliasing turns theoretically open slits into grey bands, so the physical count is optimistic.
Where it stops holding
- Solid, hole-free, single-stroke marks can go far smaller than a building with teeth and windows. One edge length cannot police a whole set.
- If icons scale with a larger system type size they get a temporary reprieve; if they are locked to a pixel size while type grows, the reconciliation worsens.
- Print and very high-density displays pack more pixels into the same millimetre, so the floor moves down. An edge length written in pixels will not travel across devices.
- This only answers when part count makes the picture melt. It does not say whether a small size needs its own master, and it does not bring the tappable region into the account.
Applying it
- Cap each target edge length with "this many strokes, this many holes". Over budget, delete parts before shrinking.
- Subjects that are born dense — settings, filters, calendars — get a simpler substitute at the small size rather than a crammed large master.
- How to check: on a device screenshot at the target edge, count gaps still visible. Merged gaps or vanished holes mean the floor has not been met; keep cutting parts.