Yes, learning NLP is best done by systematically changing parameters one by one and seeing what happens.
The scene is interesting with what seems to have been a low standing sun, rainstorm clouds and a rainbow. Got a capture with similar lighting conditions, but in digital, and it has the high contrast, but strangely, your negative seems to have only slight variations of density. Strange, but worth exploring imo.
The following procedure has helped me exploring:
- take a (difficult) shot and create a bunch of virtual copies
- use one colour model and all the presaturation levels per row
- repeat for other colour models
- Pick the one closest to target and repeat converting with different border buffer or crop sizes
- Convert using different WB settings (I have negatives that turn out best without setting WB)
See here: Improving scanning for low contrast negatives - #7 by Digitizer