I am having some difficulties calculating exposure when photographing at dawn and dusk, as exposure times are long and light changes rapidly. What I would like to is to come up with a good approximation that can yield acceptable result. I am using color transparency film, so exposure has to be fairly accurate.
I usually shoot at around EV 1 to 5 (8 min at f32 to 2 min at f64?). By the end of exposure time, the light level has increased or decreased by 1-2 stops.
My question is: Is there a good shorthand method of measuring during exposure and compensating exposure time as the light changes?
Kind regards, Lars (at the moment in outback Australia)