The indicator must appear when collection starts

What it is

Indicator onset latency is the interval between a sensor producing usable data and its status signal appearing. If indication trails recording or imaging, an unannounced collection window already exists and brief access may escape observation entirely. “Immediate” means no later than data availability to the application, with enough visible duration for short pulses to be perceivable.

Why it happens

Sensors, permission mediation, callbacks, and rendering occupy different threads and hardware paths. An application event triggered after data receipt accumulates scheduling, animation, and refresh delay, allowing collection to win a race. Switching indication before resource grant, or coupling both through one atomic state machine, removes the capture-before-notice window. Offset also matters: the light must not clear while buffered samples remain available.

Studying it

High-speed video, audio timecodes, or hardware traces can record output and indication together and estimate onset and offset distributions rather than relying on observation. Tests need cold start, contention, background wake, rapid repetition, concurrent clients, and very short samples. Means hide dangerous tails; high percentiles or maxima and pulses without perceptible indication should be reported separately.

Where it stops holding

System synchronization and human visibility differ: a technically simultaneous flash lasting milliseconds may remain unseen. Holding a signal briefly after capture can preserve perception if system detail distinguishes recent from active use. Some sensors power continuously for system functions; indication should map to disclosure of personal data to an application, not every electrical state.

Applying it

• Enter visible-indicator state before handing a data handle to the application, then revoke data before clearing indication.
• Set a minimum visible duration for brief access while distinguishing recent and current use in system detail.
• Do not depend on an application animation-completion callback for a security signal vulnerable to main-thread delay.
• Time-align sensor data, grant events, and display frames under load and pulse tests; block release for any data preceding indication or entirely invisible access.

Related

• Same group: O2.03.1 Collection needs an indicator the application cannot suppress · O2.03.3 Indication is especially important for background collection · O2.03.4 Hardware lights resist spoofing and suppression better than software icons · O2.03.5 An indicator works only where users naturally look · O2.03.6 One light for multiple sensors obscures what is collecting · O2.03.7 Users must learn what the indicator means
• Adjacent: O2.01 Permission-prompt information design · O3.05 Security-warning fatigue and disregard
• Search terms: indicator onset latency · sensor timing · minimum display duration