I use a Porta-Trace 8x11" LED light box. I have another cheaper one from ebay I use for sorting slides etc, but it’s around 7-8800K and probably a low CRI. The Porta-Trace gives good color.
The exposure times are generally around 1/4 to 1/15 second, which is the range where shutter and mirror vibration are at the worst. To counteract this I use live view and a 2 second self-timer delay, which works well.
I used to use a flash for the light source, but now prefer the light box because I can leave the aperture at f8 or f9 and just adjust the time. In addition, it means I don’t need a separate focusing light. I also found that it was difficult to get even lighting across the frame for medium and large format film, although it worked okay with 35mm.
I don’t know about the math of just inverting the curve, but it does seem to work reasonably well.
I’ll dig up a suitable raw file shot from a color neg.