All-caps and small type need extra tracking to stay distinguishable

What it is

A face ships tracking calibrated for lowercase body. Switch the run to all-caps and the letters become equal-height blocks; the default seams look tight, and neighbouring verticals fuse into a black bar. Drop the size to caption or badge territory and the same seam is fewer pixels; anti-aliasing then muddies it, and identification fails first. Tracking for caps and small type opens a seam for those two exceptions. It is not a licence to loosen body copy.

Why it happens

Capitals are optically fuller. H, I, M, N pack verticals; side bearings budgeted for lowercase x-height sit tight on those forms. A little positive tracking reopens white between the stems. Small type is a resolution problem: seam width is a fraction of an em, and as size falls that fraction drops into subpixels the grid eats. Opening the seam a little lifts that white back toward a whole pixel. Both moves look like “add tracking”; the causes differ. One is a change in coverage, the other a change in pixel budget. One value slapped on both a large all-caps title and a 10-pixel caption will be too loose for one and still muddy for the other.

Where it stops holding

Small Han sometimes needs a seam so strokes separate, usually less than Latin caps need; do not copy Western caps tracking onto Chinese. Real small caps are separate glyphs, not shrunken capitals, and already carry their own bearings; stacking letter-spacing on top tends to overshoot. When the user enlarges type, tracking that was meant for small sizes enlarges with it and starts splitting words, so this track should be bound to the small-size bucket, not glued to a component forever.

Applying it

• Give all-caps labels their own slightly open track. Lowercase body must not inherit it.
• Paint the face at caption size on dark and light grounds and look at H, M, and the digit 8: if counters still separate, do not add insurance tracking; add seam only after they fail.
• Drop small-size tracking when the type bucket changes, so it cannot ride up into a display title.

Related

• Same group: F4.12.1 Tracking that is too tight collides glyphs; too loose breaks the word · F4.12.2 CJK usually needs no extra tracking; the em box already holds the gap · F4.12.4 Uneven word spacing in justified Latin runs creates rivers
• Nearby: F4.11 All-caps text · F4.07 Typeface choice
• Search terms: caps tracking · small type letter-spacing · legibility tracking