I have been trying to use the DNG Profile Editor to create an inverted tone curve to import a color negative. I want to create an inverted linear tone curve when I convert the negative and use the downstream software to apply the appropriate camera curve. The issue I face can be replicated by doing these steps:
Go in to DNG Profile Editor. Tone curve tab, select "linear" for the base curve. If you create your own custom curve and export the .dcp file and read it in with the color tables external profile, you can see the curve you expected. It works as you expect for any curve even negative curves unless you select 'linear'. Then, if you repeat the same process except this time you draw an inverted custom tone curve (so the image goes to/from negative to positive) and export the .dcp curve and view it, the curve includes your inverted curve, but also includes the base curve (as though the 'base curve' menu had been selected)...which it should not include. It seems to be a very difficult if not impossible task to get an inverted linear line for the tone curve which makes it impossible to do any scientific measurements with a negative image.
I want to report this as a bug and request a fix.