> I think this project is particularly clever:
> http://hem.passagen.se/communication/freq_c.html

Often a trade-off is made between resolution and measurement time or the
time to accumulate a particular number of pulses, but different methods can
be used at different frequencies

IOW, simply put, a very slow frequency can be measured by capturing it
as an event with good resoltion (as a % compared with its period), whereas
a frequency too fast to measure directly can clock a counter within a set time
or to a particular value (eg rollover) which is timed. That method can lose
part-periods of pulses, although extending measurement periods will give
more accurate results, if your'e prepared to wait

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