.NEF Files Thumbnail Preview not Showing

Because Apple does not currently support the Nikon Z8 camera RAW images in any operating system including Sonoma 14.1.2. Since we are fellow users, we have no information when (or even if) Apple will support the Z8.

I cannot explain why that Z8 raw image icon appears as it does from your screenshot unless you have it associated with an application that I do not have installed, as my Z8 icon shows the normal Preview application icon.

With each Sonoma update check the option+ menu+System Information… : Raw Support category for supported Nikon cameras, or Apple's living document for Sonoma camera RAW: Digital camera RAW formats supported by iOS 17, iPadOS 17, and macOS Sonoma - Apple Support

There are free alternative applications that can view the Z8 raw files if Nikon doesn't provide one:

• Adobe DNG Converter (converts to .DNG format which is viewable as icons, Quick Look, and Preview)
• XnView MP (no conversion, just displays the raw image)

The Image viewer in Windows 11 Pro displays the RAW Z8 images (probably just the encapsulated JPG) in a window, but the tiny icons have no image.

The issue is the 'lossy' compression in the .NEF files that made its debut with the Z9. You can select 'lossless' compression on the camera and the .NEF files work as expected -- at the cost of larger files.

Try booting into Safe Mode then restart normally. Sometimes that will fix anomalies.

Use safe mode on your Mac - Apple Support

Apple has a footnote for the Z8 camera in the camera RAW support for Sonoma 14.4.1:

⒌ Lossless RAW format only.

The .NEF support is not universally identical for all Nikon cameras. Each camera has a different .NEF implementation. Only Apple knows when or if a future macOS update, or pushed camera RAW support will resolve this Finder imaging issue.

I don't know why it changed, but I know exactly when so I have to believe it's directly related. The day I bought my Nikon Z8, and from the first upload of images I took with that new, mirrorless body, the "Preview" of the image changed to the icon for NEF. Before I bought my Z8, I was using the D750, the D500 and the D850 - all of which reflected "Preview" of the NEF files, 100% of the time. Using my new Z8 changed that.

Is it only the Nikon Z8 that Apple doesn’t currently support or is it the entire Z line of mirrorless bodies?

I have no problem with the Z5 nor the Z7ii. The only camera that produces RAW files with no preview is the Z8.