To do this, set up a controlled scene with:
- A MacBeth Color Chart, for the gray scale and color swatches
- A clean, polished chrome object, for Dmin
- A large area of black velvet,for Dmax
- A person, for flesh tones
Shoot a bracket of this scene and process in your normal fashion. Make sure you color balance your film for your lights. Mount the film on your scanner and
- Use the black velvet to set the shadow endpoint
- Use the polished chrome to set the highlight endpoint
- Use the gray scale to set the RGB curves for neutral gray throughout the density range
- Use the color swatches to verify your RGB values (MacBeth color charts have very useful RGB info on the back of the chart)
- Use the person to verify correct RGB skin tones and to visually evaluate the scan
After you've made a few test scans and have dialed in your settings, save those settings for that film type.
Then, when it comes time to scan a batch of that film, you've got an excellent starting point.