To do this the iris is opened fully and exposure duration is limited to long times of more than 1/30 second or so.

Why was there no apparent effect of exposure duration on MR incidence?

A shutter-an electronic or spring-actuated mechanism that controls exposure duration.

Practically speaking, this may not be important except at very brief exposure durations, but it is as well to be aware of the problem.

Thus, by reducing their exposure duration and level to the causative agent, the probability of suffering another reaction is lowered.

Toxicokinetic profiles can change with increasing exposure duration or dose.

Also, one must consider temperature, exposure duration, and sheltering effects.

This would allow recovery processes to take place during the quiet interludes that are gained by increasing the exposure duration.

Inspection time refers to the exposure duration required for a human subject to reliably identify a simple stimulus.