Exposure time and capture volume share fields but answer different questions. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Exposure time and capture count are different ledgers

The first schedule has 4 fields at dwell time 5 s, so exposure time is 20 s. With 3 channels it records 12 captures.

t=45 s=20 s,Ncap=43=12t=4\cdot5\ \text{s}=20\ \text{s},\quad N_{\text{cap}}=4\cdot3=12
Exposure scheduleFields and channels set capture and time budgets.dwelltotal4 fields12 captures5 s20 s

Equal exposure time can hide a different capture count

The second schedule changes to 5 fields at 4 s, so the time is still 20 s. The channel count is 2, giving 10 captures.

t=54 s=20 s,Ncap=52=10t=5\cdot4\ \text{s}=20\ \text{s},\quad N_{\text{cap}}=5\cdot2=10
Exposure scheduleFields and channels set capture and time budgets.dwelltotal5 fields10 captures4 s20 s

More fields can shorten time but expand captures

The third row uses 6 fields and dwell time 3 s, giving 18 s. Its 4 channels produce 24 captures, so the scan separates time budgeting from readout volume.

t=63 s=18 s,Ncap=64=24t=6\cdot3\ \text{s}=18\ \text{s},\quad N_{\text{cap}}=6\cdot4=24
Exposure scheduleFields and channels set capture and time budgets.dwelltotal6 fields24 captures3 s18 s