I would like to take long exposures with the Agfa vista 400, but I do not know how to calculate for the additional exposure time needed to compensate for reciprocity failure. I have also looked up the data sheet for the film, but instructions for compensation for exposures longer than 2 seconds only include recommended aperture adjustments. No guidance is provided regarding adjusting exposure times instead.
There is also this technical guide for many of Agfa's films, but the charts were incomprehensible to me.
A table of adjusted exposure times or any help would be much appreciated.