batch converting .nef to tiff

If your version of macOS supports the RAW format, you can either batch convert them with Preview, if they are in folders on your Mac, or if you imported hem to Photos you can export them from Photos as TIFF files.

• With Preview:
  • The preferences in preview should be set to "Preview > Preferences > Images: Open groups of photos in one window".
  • Select all photos in the Finder at once, ctrl-click or right-click them, the use the command "Open with Preview". All selected photos will appear Preview in one window in the sidebar.
  • Now select all photos in the sidebar with ⌘A and use "File > Export". In the export window select TIFF as the format. click the Options button to select the TIIF options.
• With Photos:

  Import all RAW files to Photos, then select them at once with ⌘A and use File > Export to export the batch of photos as TIFF files.

To do them outside of the Library use an Automator workflow app like this one:

It's automatic and looks like this:

It is the same with the RW2 format from my Lumix camera. Preview can batch convert the format to TIFF on export, but not batch edit it. I hope this will change soon.

Which Nikon model are you using? Is the RAW format of the camera supported by your version of MacOS X?

And which version of MacOS X do you have installed?