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When I open a Nikon RAW .NRW file (16-bit image) with Preview, and select "File > Export...", when the Format setting is set to HEIC, the Depth option for "16 Bits/Channel" is grayed out. Why? I can export as PNG or TIFF with 16-bit depth, so why not HEIC?

And, what software can I use to convert .NRW files into lossless 16-bit .heic files?

(I am using MacOS 11.3.1)

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Apple doesn't appear to support 16-bit HEIC.

I can't find anything official on this, but I can find a whole lot of user complaints bemoaning it.

https://discussions.apple.com/thread/251072024

I'd be seriously tempted to try Nikon's own ViewNX-i [freeware] to do your conversions. Though as yet it doesn't support HEIF at all, it is far better at interpreting Nikon RAW files than any other app. Overall you will probably lose less information going NRW > ViewNX-i > PNG than you would via Preview, or even Photoshop.

BTW, NRW isn't 16-bit, it's 12-bit. Nikon's higher spec RAW file NEF is 12 or 14-bit.

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  • Thanks for the info. I'll take a look at ViewNX-i or NX Studio. I'll file a bug report with Apple since saving a 12-bit NRW to 8-bit HEIC cannot be "lossless," therefore the "lossless" position on the quality slider in Preview's Export pane shouldn't be available for >8-bit images.
    – Not22
    Commented May 11, 2021 at 3:49
  • Oh, thanks for the heads-up on NX Studio. I'd missed the announcement about its release. I'll be checking that out myself, today.
    – Tetsujin
    Commented May 11, 2021 at 5:06
  • Late shout on this - Studio is still rather new & doesn't support multiple monitors [hopefully it will in future], so if you need that, stick with NX-i for now. [You can't have both at once, I had to go find an older installer to go backwards again.]
    – Tetsujin
    Commented Jul 18, 2021 at 17:39

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