I don't have an answer, but if you intend to use a flatbed scanner - any flatbed scanner, even a high-end Epson - you will get significantly better results photographing the slides. Better resolution, and much less chromatic aberration (colored fringing), which is the real curse of flatbed scanners.
Flatbed scanners never deliver the optical resolution they promise. You get the pixels, but not the detail. For a 35mm frame, you can expect at most 3500 effective pixels long side. And even that will be full of CA you can't correct, because it doesn't follow a regular pattern, like it does through a camera lens.
All you need is a good, flat field macro lens. If you happen to shoot Nikon, the Micro 60mm/2.8 has absolutely stellar performance for this kind of work.
And then you can get your camera profile.
I ran my first tests with vuescan software and the scans are stored as DNG files without any color processing.
I also have IT-8 targets for slide calibration, but lightroom, as far as I know, has no capability to create an "camera profil" for these target.
Why not create and apply the IT8 profile inside Vuescan and be done with it.
You're probably better off using TIFF file format:
I abandoned my film scanner years ago and use a DSLR setup with a 1:1 Macro lens and process the camera raw files in LR. It's 100x faster, provides superior image quality (Live View focusing), and with a diffused light source grain, dust spots, and scratches are practically eliminated. Unlike film scanners there's little need for IT8 calibration using a DSLR with slide film. Kodachrome slide film will need a Blue Correction Tone Curve, but that's about all and other slide films should look good with minimal color correction inside LR. If you're talking negative film that's a whole other story:
Yep, that's about what I had in mind.
And my own experience is also that very little color correction is needed. However, the tone response curve can be a bit tricky, it tends to come out at the heavy, too contrasty side. But I've also found that Lr's Contrast slider responds well to this, in combination with Blacks and Whites to maintain the endpoints.
A little experimenting is needed, but nowhere near the amount of work a scan requires.
I also find -Highlights = + Shadows helps to correct the tone response curve. With a dense film like Kodachrome I start with a Blue correction Tone Curve (not needed for other slide films), -25 Contrast, -50 Highlights, and +50 Shadows using Adobe Standard. I then use Highlights & Shadows presets to tune those settings and finally set the Whites and Blacks clipping points. WB usually needs just a slight tweak and then it should look pretty good. This is using a speedlite with 5500K color temperature for the light source.
@trshaner, @D_Fosse, thank you for your support. I have an artix 4k slide / negative scanner for this purpose.
I understand, that using an duplication setup will speed up the whole prosess and I will give it a try to find out the best way for me.