JPG to NEF Converter

Encoding: the JPG uses lossy DCT coding in 8×8 pixel blocks, with colour usually stored at half resolution; NEF uses uncompressed, lossless compressed, lossy compressed, or High Efficiency on recent Z bodies, and the download is a Linear DNG: demosaiced 8-bit RGB with the colour matrices raw editors need.

Bit depth: 8 bits per channel in the JPG; NEF allows 12 or 14 bits per channel, and the DNG written here has 8 bits per channel, linearised.

Colour: YCbCr shown as RGB, greyscale, or CMYK from print software in the JPG; NEF supports camera RGB from a Bayer mosaic, written here as 8-bit sRGB.

Metadata: the JPG can carry EXIF (camera, date, GPS), XMP, IPTC and an ICC profile in APP segments; NEF can carry EXIF and Nikon maker notes, partly encrypted, plus a thumbnail and a larger preview, but nothing is copied across.

JPEG is the universal photo format. It compresses by discarding fine detail the eye is least sensitive to, which makes photos small but blurs sharp edges and text if pushed too far.

A JPEG starts with the bytes FF D8 and is a run of marker segments: APP1 carries EXIF and often a thumbnail, APP2 an ICC profile, DQT the quantization tables that decide the quality, and SOS the compressed scan, which ends at FF D9.

JPG files usually come from cameras, phones, scanners and almost every app that saves photos.

NEF is the raw format of Nikon cameras, from the D1 to the current Z series. It stores 12 or 14-bit sensor data, uncompressed or compressed, with a JPEG preview the camera renders using its Picture Control.

NEF is TIFF-based: the first directory usually holds a small thumbnail, and sub-directories hold the sensor data and, on current bodies, a full-size JPEG preview. Nikon's maker notes are a TIFF structure of their own, and since the D2X their white-balance block is encrypted with a key derived from the camera's serial number and shutter count.

NEF files come from Nikon DSLRs (D-series) and Z-series mirrorless cameras.

Forms and workflows that ask for NEF usually feed a raw editor, and each of those opens DNG as well, so the DNG can take the NEF's place. Keep the JPG if you only need to view or share the picture.

What NEF offers when it comes straight from the camera: Lossless compressed mode with no data loss; Picture Control recorded so Nikon NX Studio can reapply it; 12 or 14-bit sensor data. Its drawbacks: Partly encrypted maker notes; The lossy compressed mode discards some sensor data; Large files on high-resolution Z bodies.