A long, long time ago, I used to host a set of Photoshop actions to facilitate processing of negative film scanned with a DSLR or other digital camera (which, when well done, provides results that are far superior to those from all but the best dedicated film scanners).
I removed those actions for a variety of reasons. However, I have decided to make them available once again. They can now be downloaded from this OneDrive link.
The actions are provided without support. The process is very straightforward for anyone who has used Photoshop before. It is essentially a non-linear inversion, a curves layer to normalize the individual R/G/B channels (assuming we’re talking colour film), and a second curves layer to allow for global contrast and brightness adjustment.
Note that you *may* need to correct for white balance, which can be done on the second curves layer using the grey eyedropper tool. Otherwise, this action will get you where you want to be.
Again, I cannot provide support for this action. If you have questions, I can try to provide some answers, but I cannot guarantee success unless you know how to DSLR scan properly.