Information density must follow viewing distance

What it is

The same public screen can carry only a few large blocks at ten metres, and a list with control labels only at half a metre. Density follows distance. Far range gets a sparse, high-contrast, glanceable layer; secondary information and operable detail wait for near range. Visual angle sets this, not resolution—4K at twenty metres is still unreadable grain. This entry does not assign touch versus gesture at a given distance, and it does not treat chatter in the mode switch.

Why it happens

Angular size on the retina falls with distance. Type, stroke, and spacing set for a face-on reader collapse into texture far away, and attention cannot seize any one item. Type set for far range as three giant lines greets an approaching person with an empty poster and nowhere to land a near action. A public screen’s audience sits in several distance bands at once. One fixed density can serve only one band; everyone else cannot read, or feels neglected.

Density therefore has to be a function of distance, not a compromise medium. The far layer answers the one question a passer-by can use. The mid layer gives structure and whether walking closer is worth it. The near layer spreads controls. Vogel’s public ambient displays unfold detail on approach because visual angle and dwell grow together. People do not automatically walk in to resolve a line of small type. If the far layer already failed, the walk never starts.

Studying it

Mark typical viewing bands on site. Compare the same content at a fixed density with density that switches by band. Intercept in each band: items read, items misread, whether an approach followed. Ten-foot readability tests for television are cousins of the far band, but a public screen also has a passing-by band and a face-on band; a single sofa distance is not enough.

Independent variables: item count and minimum type in each band, whether density follows measured range, whether detail unfolds or hard-cuts on a switch. Dependent variables: correct reads per band, walk-in rate from far to mid, whether a landing for action exists up close.

Parking people on a lab line overestimates readability at that line; they are not hurrying. In the field, use a glance inside crossing time, not a settled read. Do not treat the panel’s physical resolution as the density cap. The cap is visual angle at the farthest distance that still counts as viewing.

Where it stops holding

A screen that only ever serves one viewing distance (a clerk-facing counter display, an instrument cluster) can lock a single density. An emergency alert has to be readable as an alert at every distance; it cannot wait for approach to turn decoration into words. A legal or accessibility floor on type size is a near-band floor and must not be shaved by “far range should be sparser” into unreadability up close—the near band still has to work at face-on. A decorative media wall that does not ask to be read is arguing atmosphere, not transmission; change the measure.

Applying it

• Write an information budget for passing-by, stopping, and face-on: at most one or two giant items while passing; structure and a stay-or-go judgement when stopped; lists, fields, and control labels only at the glass.
• Back-solve minimum type and maximum item count from the farthest useful distance, then add detail near. Do not shrink the near UI and play it at far range.
• When density switches, keep the one or two items already seen on screen. What arrives is an unfolding, not a full-frame replacement that looks like different content.
• Verify by asking people who did not design it, at each of the three distances, “what is the one thing that matters now, and what can you do next.” If a band cannot answer, cut items and raise type in that band before adding chrome.

Related

• Within the group: K7.05.1 Distance selects which input is available · K7.05.2 Switching thresholds need hysteresis
• Adjacent: K5.03 Ten-foot readability · Z8.01 Ambient displays and peripheral information · K7.01 The Passing-by Effect
• Search terms: information density · viewing distance · visual angle · ten-foot UI