Letting people set distance is more reliable than one universal preset

What it is

Products default a panel to “1.5 m, dead ahead”. That number may pass for the average participant and fail for myopia, for a seated person, for someone still finding focus after donning. User-adjustable viewing distance hands distance to the wearer, which is more reliable than refining another universal preset. The issue is not whether that preset should be nearer or farther. It is that a preset as the only answer fails, and adjustment as a capability has to exist.

Why it happens

Comfortable distance is the intersection of personal variables: refractive error and glasses, IPD, the headset’s focal plane, sit versus stand, arm length, current fatigue. A “recommended distance” calibrated on young emmetropic lab participants does not survive that intersection. People adjusting in the moment use immediate clarity and pressure, closer to current state than any metre figure written in advance. Adjustment also covers posture change: after sitting, eye height and reach both move, and the standing distance is now wrong. With no adjustment entry, people pay with the body — lean in, step back, tilt the head — spending neck and lumbar on the slider the designer omitted. What is being adjusted is distance; whether angular size follows is a separate decision. Distance-only with centimetres locked lets people drag the panel so far that type dies, without understanding why.

Studying it

Compare a fixed preset, a few discrete steps, and continuous adjustment, across refractive status, sit/stand, and session length, on reading and pointing. Where people stop, and how they perform after stopping, are the data.

Independent variables: adjustment mode, whether angular size is locked while adjusting, starting distance, posture. Dependent variables: distribution of final chosen distance, number of adjustments, reading and pointing performance, count of body-compensation moves (lean / step back).

Individual difference is the unit of analysis: report the distribution and quantiles, not only the group mean. A mean that lands on the preset does not mean the preset was good for each person.

Where it stops holding

When safety or measurement requires the panel to register to a real surface, distance cannot be dragged freely; adjustment slides on that surface. People with no depth perception, or who cannot grab, will fail at continuous drag and need larger/smaller steps. On a world-locked panel shared by several people, one person’s distance change is a change for everyone and must be an explicit shared control, not a private preference. For children and highly varying stature, the default start should scale with height rather than sit at an adult 1.5 m for them to drag from scratch.

Applying it

• Give reading panels a grab or a slider. The default is a start, not a lock. Persist last chosen distance as the next start.
• Lock angular size while distance is adjusted, so people do not drag the panel away, shrink the type, and conclude they adjusted wrong.
• On sit/stand change, prompt once “replace this?”. Do not assume the last posture’s distance still holds.
• How to check: have several people, differing in refraction and posture, wear it for ten minutes. If most hunt a body pose instead of using adjustment, the entry is not visible enough. If chosen distances spread wide and performance still passes, the universal preset must not be the only answer.

Related

• Same group: N3.09.1 Angular size is the design variable, not physical size · N3.09.2 Very few depth layers remain usable · N3.09.4 Comfort viewing distance narrows toward mid-range as the session lengthens
• Nearby: N3.02 Interface Distance · N1.04 Vergence–Accommodation Conflict
• Search terms: user-adjustable viewing distance · personal comfort distance · egocentric distance