The NEF file (.nef)

NEF is the raw format of Nikon cameras: the D-series digital SLRs since the D1 of 1999, and the Z-series mirrorless cameras. When the camera is set to RAW (or RAW + JPEG), each photo is saved as a .nef file holding what the sensor recorded, with the camera's settings stored alongside rather than applied.

Raw means the data comes from before the camera has made a picture. A sensor sees only brightness, through a mosaic of red, green and blue filters, so each photosite has one colour value. To make a photo, software has to estimate the two missing colours at every pixel (demosaicing), apply the white balance, convert the camera's colours into a standard colour space and apply a tone curve. Nikon describes white balance, hue, tone and sharpening as "instruction sets" stored in the file, which you can change later without touching the sensor data.

• More levels. A NEF holds 12 or 14 bits per photosite: 4,096 or 16,384 levels, against 256 per channel in an 8-bit JPG. That's what lets you rescue shadows or pull back highlights.
• It looks flat at first. A raw file shown with neutral settings has less contrast and saturation than the camera's JPEG, which had a picture style applied. That's expected, not a fault.
• A JPEG is hidden inside. Each NEF carries JPEG previews, which is what the camera's screen, thumbnails and quick viewers show. That's why a NEF can look right in one app and different in another: one shows the preview, the other renders the raw data itself.
• It's a capture, not a delivery format. Nobody can view a NEF in a browser or most phone apps. Export a JPG, HEIC or PNG to share.

Nikon cameras offer several ways to store the raw data. Which ones you get depends on the model. On a D850, for example, the menu has three, and the manual describes them like this:

High Efficiency raw arrived with the Z9 and is based on TicoRAW, a raw codec from the company intoPIX. Nikon says HE* files are visually identical to lossless ones; HE files are smaller again. Photography Life lists the Z9, Z8, Zf, Z6III and Z5II, all with Nikon's Expeed 7 processor, among the cameras that offer it, and measured HE* files at roughly 30 MB against about 50 MB for lossless compressed, with no visible difference in its tests.

Shoot NEF when you'll edit the photo: exposure and white balance can be changed far more than in a JPEG. Shoot JPG or HEIF when you need finished pictures straight from the camera. RAW + JPEG gives you both, at the cost of card space. DNG is a raw format with a public specification; converting NEFs to DNG is a common archiving choice, since the US National Archives recommends it for proprietary raw formats like NEF.

• Nikon NX Studio (free, Windows and macOS): Nikon's own viewer and raw editor. It replaced ViewNX-i and Capture NX-D in 2021 and applies the same Picture Controls as the camera, so its results match the camera's JPEG most closely.
• Adobe Lightroom, Lightroom Classic and Photoshop (Camera Raw): the most common choice. Capture One, DxO PhotoLab and Affinity Photo also read NEF.
• Free and open source: darktable and RawTherapee on Windows, macOS and Linux.
• Just looking: macOS Photos and Preview, and iPhone and iPad Photos, open NEFs from cameras on Apple's supported list. On Windows 10 and 11, install Microsoft's free Raw Image Extension for thumbnails in File Explorer and viewing in Photos.
• In the camera: most Nikons have a NEF (RAW) processing item in the Retouch menu that saves a JPEG copy with new settings.

To convert a whole folder, use the export in NX Studio or Lightroom, or the command line. These commands use ExifTool and darktable's command-line tool:

# pull out the embedded JPEG preview (no raw processing)
exiftool -b -JpgFromRaw DSC_0001.NEF > DSC_0001.jpg

# render the raw data to a full-quality JPEG
darktable-cli DSC_0001.NEF DSC_0001.jpg

# list the camera settings and maker notes
exiftool -a -G1 DSC_0001.NEF

• The camera is newer than your software. Each new Nikon model needs explicit support, because the details change from camera to camera. Update the app. If you can't (an older Photoshop or Lightroom, an older macOS), convert the NEFs with Adobe's free DNG Converter, which Adobe offers precisely for backward compatibility; older versions open the DNGs.
• **It's an HE or HE* file.** See the note above: the app may support the camera but not the High Efficiency codec. Shoot lossless compressed, or use an app that supports HE.
• It opens, but looks different from the camera's screen. The camera shows its own JPEG rendering with your Picture Control. Other apps render the raw data with their own defaults. Use NX Studio, or pick a camera-matching profile in your editor.
• Only a small or low-resolution image appears. The program read the file as a plain TIFF or showed an embedded preview. Use a real raw converter.
• The file is damaged after a copy. A NEF cut short (by removing the card too early) often still shows its preview but fails to decode. Copy it again from the card if you still can.

A NEF can't run code, but it carries a lot of metadata, and people sending raw files to a client or a forum rarely check it:

• The camera's serial number, in the maker notes (and often the standard Exif serial number tag too). It ties every photo to one body.
• The shutter count: how many photos that body has taken so far, which is why it's often checked when a camera is sold second-hand.
• Location, when GPS was on (a GPS unit, or location from a phone through Nikon's app).
• Owner and copyright text you typed into the camera's menu, plus date, time, lens and every setting.

Check with exiftool -a -G1 file.nef. Stripping all metadata from a raw file isn't a good idea: the maker notes are needed to render it correctly, and the serial number in them is also the key to the encrypted blocks, so deleting or changing it can leave colour data unreadable. Remove location with exiftool -gps:all= file.nef, and when the serial number or shutter count matters, share an exported JPEG with its metadata stripped instead.