considering we are white balancing off of the base emulsion (which is a consistent colour) and not the scene, theoretically, should/could the white balance value be the same across every scan?
Taking white balance off of the film base is the recommended procedure for camera scanning.
While the WB of one film is mostly the same from start to end, WB of different films can vary depending on film type and development. This means that we can take one WB reading per film, but should take a new reading for the next film.
Just out of interest - you’re talking about B&W negatives here? Certainly the base can vary pretty widely, take chromogenic films for example. Colour negative varies hugely of course.
Edit: Sorry, you must be talking about colour negative as NLP doesn’t use WB for B&W, my mistake. The orange base on colour negative can vary a lot. Printing in the dark room back in the day meant using quite different filtration for certain films.
Thanks both, interesting stuff. Been doing some testing and found that leaving the default white balance from the Nikon 9000 / Vuescan / Lightroom DNG (6500 temp 10 tint) gives me colours that are ‘better’ to my eye. Also locking the RGB exposure to 2.2 gives me perfect histograms every time. (Appreciate some of this probably belongs in the different thread but was seeking advice on white balance initially and figures this thread gets the most traffic).
The extent of a white balance adjustment can vary from one roll of film to the next as there can be differences from batch to batch of film and from one development session to the next, despite all the best care and technology devoted to maintaining uniformity. Therefore I redo the white balance for each roll of film I convert unless I know the film batch and development batch were the same from one roll to the next.