This question already has an answer here:
On nearly every camera I've used, the scale of shutter speeds goes something like:
1s, 1/2s, 1/4s, 1/8s, 1/15s, 1/30s, 1/60s, 1/120s, 1/250s, 1/500s, 1/1000s, 1/2000s
whereas clearly a scale of halves actually runs:
1s, 1/2s, 1/4s, 1/8s, 1/16, 1/32s, 1/64s, 1/128s, 1/256s, 1/512s, 1/1024s, 1/2048s.
That's close enough, but still, there's a difference, and I imagine that with high-precison electronic shutters it's quite possible to be right on the mark with timings.
Where on the scales are the marked, nominal values generally intended to be true (i.e. where are the shutter makers aiming for true accuracy, even if it's only an aim):
- along the up to 1/8s range (where they match the actual scale of halves)
- along the 1/15-1/120s range (where they are off at a ratio of 0.9375)
- along the 1/250s and faster range (where they are off at a ratio of 0.9765625)?
I am well aware that mechanical and even electronic tolerances may in most circumstances render quibbles over tiny fractions of a second moot. I am equally well aware that many of the scales and numbers used in photography are convenient approximations, and not intended to be taken at face value.
Even so, the fact remains that in design and manufacture an approximation of an ideal still requires a conception of that ideal. Just because a standard is an ideal and can't be met, or it doesn't really matter if it's not met, doesn't mean that design and manufacture don't need ideals, or don't work with them.
I guess that the point of truth in the shutter timings scale is 1s=1s, and all the other numbers are allowed to be approximations if necessary, but it would be nice to know.