So i was reading this article on how one may use one's camera to suggest and determine the appropriate exposure duration. I got confused with Plan B - how does one extra stop stretch the exposure from 1 min to 32 min?
yes, what uncle catchlights said, use STOPS to determine.
1 stop roughly doubles, so if you look at his post,
1: ISO3200 , f11, 30 seconds
when you HALF the ISO, that is one stop less, you have compensate by doubling exposure time to 60 seconds, the next line
2: ISO1600, f11, 60 seconds
similarly, for f-stops, the same applies. multiplying by 2 is really easy.
as to how to determine, just shoot at very high iso, if the histogram looks right, then adjust accordingly.
if the light is changing, then best to compensate a little, for example, if it is transiting into darkness, remember to expose more. long exposures are no joke, you don't want to wait 32 minutes to get nothing out of your wasted time, just because you didn't know what you were doing.
oh i see where i got "misled"; I was looking at Plan A's timings and thought 1 min was the max exposure at 5 stops, and took that as the baseline for Plan B. That is not correct, as Plan A was able to "stabilise" with a 2-second exposure, whereas Plan B was still asking for more than 30 seconds since there's not enough light. thanks