1508. Why is TTG’s limit for combined exposures in P5 “one second” instead of some longer period?

There are three reasons for the “one second” limit, all of which reinforce the purpose of P5 (which is to ensure that every TTG-qualified photograph represents “one moment”; see #1501):

1) “One second” is the shortest universally used time unit

Day > Hour > Minute > Second

2) “One second” is universal shorthand for “a moment” (“Just a sec”).

Different countries use different units for measuring distance — e.g., some countries use meters while others use yards (fathoms and furlongs remain options as well)—

— but every country in the world measures time in “seconds.”

3) “One second” is the longest universal time unit that applies when people think of a “glimpse” of a scene (see #2401).

That is why, on both the page on photographing lightning and the page on photographing fireworks, TTG photographers are advised that they will less likely be challenged on the satode aspects of an exposure that lasted less than 1 second.

Any limit longer than TTG's “one second” would either be arbitrary (17 seconds? 29 seconds?) or — if the limit were increased to the next shortest universal time unit (“one minute”) — would lead to too many untrustworthy photographs to be acceptable for TTG’s standards.