Ah. Now I see what you’re doing.
I have a Canon CanoScan 9000F Mark 2 USB scanner for scanning
negatives and reflective photos. I also use VueScan (on Linux), and
have purchased the lifetime option. There’s also aftermarket assorted
sized negative holders for flatbed scanners.
As already stated, use the Neutral profile, both in camera and within
RawTherapee; enabling the Color DCP settings, Tone Curve, Base Table,
Look Table. You’ll also need to acquire your lens profile, from the
Adobe Camera Raw Windows package, else you’ll have some possible minor
lens deformation on side by side comparisons.
You’ll want to neutralize the negative masking to a see through clear.
Usaully, the masking is orange in color. Once the masking is see
through, you’ll have the colors usually intended with the exception of
film aging and other anomalies.
Sounds like a lot of work using a camera, along with the problem of
trying to keep the negative film flat while photographing, along with
using a caliberated backlight.
For this purpose, is why I have a Canon 9000f Mark 2 flatbed scanner
and VueScan. Using this combination, can scan negatives, neutralize
the masking (see VueScan instructions for neutralizing negative
masking) and save into a raw file for backup. Much easier and with
reproductive results versus using a non caliberated camera setup.
I have not tried any of the devoted negative scanners. From what I’ve
heard, the recent PlusTek negative scanners (similar to the famous
Nikon scanner) now have recent VueScan Linux drivers, but I have not
verified. Looks like Kodak, after ~20 years of scanning, is now trying
to jump into this market.
I scanned many types of old family photos/negatives several years ago
using the flatbed and VueScan. Scanned to raw, then produced
TIFF/JPEGS; saved to Bluray BD-R media. I also have a Canon Selphy
CP1200 for making prints on the new durable photo paper.
Would be nice to have a function within RawTherapee to neutralize the
negative masking to clear, for your purpose.