Exposure times >1s often need to be adjusted for the [reciprocity failure (Schwarzschild-Effekt)](https://en.wikipedia.org/wiki/Reciprocity_(photography)). An example by Ilford on how to calculate the adjusted durations: https://www.ilfordphoto.com/wp/wp-content/uploads/2017/06/Reciprocity-Failure-Compensation.pdf Also compare values with: https://www.denisolivier.com/long-exposure-calculator/en/
Exposure times >1s often need to be adjusted for the reciprocity failure (Schwarzschild-Effekt). An example by Ilford on how to calculate the adjusted durations: https://www.ilfordphoto.com/wp/wp-content/uploads/2017/06/Reciprocity-Failure-Compensation.pdf
Also compare values with: https://www.denisolivier.com/long-exposure-calculator/en/