Commiting to a process for post-processing scanned negatives

For invert use PS menu Image>Adjustments> Invert. You'll also need to apply Image> Auto Tone, which should get you to a fairly well toned B&W image. You can create a PS action to batch apply those two settngs using the PS Image processor. Then save the good images and delete the bad ones. You can probably get good results saving the inverted and Auto Toned images to JPEG file format for further non-destructive editing in LR. If that's not working for you upload the image file to a file sharing site like Dropbox and I'll look at it.

I import the camera raw files directly into LR and usually keep them since they are farily small compared to the final PS TIFF files saved with ZIP Layer Compression. If happy with the LR edited PS TIFF file you can flatten it, which will reduce the file size by about 45% with no affect on the LR rendering. Example Canon 5D MKII 20 Mp file:

Let me know if you have any questions. Mark and I worked on DSLR film captured color negative raw file processing techniques over a period of about two months. The two workflows outlined in the LULA article are the results of that joint research. My workflow uses LR primarily for raw conversion and orange mask removal followed by Edit in PS using an action with non-destructive adjustment layers. The resulting PS TIFF file can be processed further in LR just as you would with a normal camera image file.

Inverting scanned color negatives is much better done in Photoshop.

The Curves adjustment comes with a preset for inverting color negatives, which most of the time provides you with a good basis for further editing. The image below is obviously too dark, but that's easily fixed. You can also add more adjustments layers if you wish, like Levels and Saturation.

If you can't get the colors absolutely right, you can tweak them with the HSL panel in Lightroom.

But before saving and closing the file, remove all dust spots and scratches, this is best done at 100% view. (which is the same as 1:1 in Lightroom)

For noise reduction, you would need to select both layers, right click them, and choose Duplicate layers.

The duplicated layers will then appear (selected) at the top of the Layers panel.

Right click them and choose Merge layers. Double-click the name of the merged layer, and name it Noise reduction or similar.

With this layer selected, go to Filter > Noise > Reduce noise. Set Preserve details to a high value, like 85 or more.

If one application of the filter at max strength isn't enough, you can run it several times. Work at 100% view.

Some general tips about scanning:

• Always scan as 16-bit tiff. (the scanning software may call it 48-bit) Do not scan as jpg.
  16-bit contains 65,000 levels per channel, which gives you editing headroom, and prevents image degradation caused by editing. 8-bit contains only 256 levels per channel.
• Make sure to capture the full tonal range of the image. Look at the histogram. There should be some unused  space at both ends, which indicates that shadows and highlights have not been clipped.
• If the scanning software gives you a choice for ICC profile for the image, choose Adobe RGB.
• Some scanning software will do a decent job of inverting the image, which makes post processing easier. This may also depend on the film type.

I have done a fair amount of negative scanning. I use Vue Scan scanning software, and then when I import to Lightroom I have created a set of defaults for my scanner to apply sharpening and other settings. I don't use any other plug-ins, and find that I get reasonably good results. I am primarily looking for old family photos, and have been happy with this workflow. Not really relevant to the original question, I suppose. Just a comment about  scanning in general.

I think- Because NLP is a Plugin for Lr, that it can only modify Lr development functions, but with a neat UI to assist. So really you can do everything in Lr yourself without NLP. It is just learning how!

The one obstacle to overcome with 'Negatives' is that raw files can only be inverted in Lr with the Tone Curve, and that makes many of the Tone sliders (Exp, etc) work in reverse.  (NLP refer to this as "controls are screwy" )

And you would not be the only person wanting Lr to have a 'raw invert' function:

https://feedback.photoshop.com/photoshop_family/topics/inverting_in_camera_b_w_negative_scans_to_positives_lr4_feature_request

And as NLP claims to "Make it easy....use the “TIF Copy” option!"- so can you Export a TIF from Lr easily!

You can even start a Neg inversion with a Profile- but the sliders are still reversed:

https://www.cuchara.photography/blog/2018/5/one-click-inversion-of-color-film-negatives-in-lightroom

Make Your Own Profiles LUTs - Matt Kloskowski