Using Denoise AI as a plug-in for Lightroom Classic.
Current version (updated).
Camera: Nikon D750 File Type: NEF
After importing image into LR, and before doing any other editing, I use the Denoise AI plug-in. Use the compare option to see results of different modes. 90% of the time there is a magenta color cast/areas, often in the dark colored areas of the image - navy coats, blue jeans, black jeans, etc.
Solutions? Recommendations? Thanks!
Try using Edit in and send a TIFF, JPEG or PNG to see if that makes a difference.
FYI, I also get a magenta cast on a blue sky with Photo AI when processing a .CR3 file from my Canon R7. This only occurs with the Denoise function. Have to process to a .tiff file first using Canon DPP then import into Photo AI to work around this issue.
I am having the same issue with raw files from my Sony A9 (mk1). Yes, I can process and send a tiff to denoise AI and I don’t get the magenta patches, but that means I can’t utilize the DNG output option. I’d really like to output as DNG. Have you all found a solution to output to DNG? I can provide the raw file if you need it as well as the DNG with magenta artifact.
Have you tried the latest version of DeNoise AI which is v3.7.2 ? Apart from that you should raise a support request at the main website.
Yup. Working with the latest 3.7.2.
Will put in a ticket
I have spent days researching this issue - focused on the Nikon D750 - but in this thread it seems that it is not camera or camera brand specific. In some threads, there was discussion that the sensor on the Nikon D750 was the culprit…to take pictures with the lens cap on and see if the magenta color is present, if so the sensor needed to be replaced. Other suggested that the combination of high ISO and an underexposed image would result in the magenta cast (no numbers given for what define high or underexposed). There were comments that when shooting people indoors, with mixed lighting, and using a fill flash, there is not much that can be done. I was shooting an indoor event, no windows, very large building with tall ceilings, mixed temp overhead lights, all lights on so not dark, using Nikon D750, Nikon 24-70mm f/2.8, Yongnuo 968N with Godox AK-1 accessory (‘flash bender’), on a Custom Brackets Pro-M bracket. Images taken of people within a say 10’ distance were ok - the image of that person but anyone standing behind them had a skin tone that looked like muddled, tan leather with a magenta tone. Dark blue or black clothing had areas of magenta. When taking overall shots, the skin tones of all people/clothing in the image had the same issues. I shot a line-dancing performance at a senior center the next day under similar conditions - the room was much smaller -and had the same results. My highest ISO was 1200 which; the D750 has a good reputation (at least I thought) of being able to handle noise so I was not overly concerned - thinking that using Denoise AI in post would virtually eliminate any noise without issues. Not sure where the problem lies - and perhaps it is with the person pressing the shutter 
I suspect it isn’t with the person pressing the shutter, I suggest raising a support request at the main website.
Nikon D750, Nikon 24-70mm f/2.8, SS 1/200, ISO 500, f/8.0
Top Image: Original RAW image - as I look closer at this file, I can see some of the magenta.
Middle: LR adjustments
Bottom: Shows magenta areas in jeans, especially in the black shirts - after processing thru Denoise AI.
Well it is a way underexposed image. Your pushing the boundaries, use Edit in from LR with it’s adjustments and send a TIFF to DeNoise.
Yes - it is underexposed. Indoors, mixed lighting, only able to use OCF on bracket (no light stands for safety reasons or would have used Godox strobes), trying to freeze actions of dancers (1/200), use an aperture that would provide for focus of dancers and residents (f/8.0) while keeping the ISO low (ISO 500) to reduce noise. I have primes with f/1.4 and f/1.8 but needed the zoom functions. Any suggestions on settings that would have worked better?
I am also observing color shifting when using Photo AI to sharpen soft faces, but only in the preview window (split pane) - the exported images don’t appear to have it, so perhaps it’s something in the UI rather than the algorithm?
As a follow up to my ticket, Topaz customer support has been very respectful and responsive. I’m looking forward to figuring this out
As you said you have an aperture to maintain the DOF the option you have left is to increase the ISO, in this situation I would probably use ISO2000 because it looks like you need at least ISO1600 and maybe just push the speed up to 1/250 to compensate.
It is important to match the exposure triangle to the situation, nowadays the software available can remove noise at that level easily.
