BMP to NEF Converter

Encoding: the BMP uses usually none; RLE for some 4 and 8-bit files; 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: 1, 4, 8, 16, 24 or 32 bits per pixel in the BMP; NEF allows 12 or 14 bits per channel, and the DNG written here has 8 bits per channel, linearised.

Colour: RGB or an indexed palette in the BMP; NEF supports camera RGB from a Bayer mosaic, written here as 8-bit sRGB.

Transparency: the BMP stores it as an optional fourth byte in 32-bit files, which many programs ignore; the DNG has none, so transparent areas are filled with the colour you choose.

Metadata: the BMP can carry nothing beyond the header's resolution fields (and a colour profile in rare V5 headers); NEF can carry EXIF and Nikon maker notes, partly encrypted, plus a thumbnail and a larger preview, but nothing is copied across.

BMP stores raw, uncompressed pixels. Files are huge but trivially simple, which is why some legacy Windows software, embedded displays and printers still ask for it.

A BMP is a 14-byte file header ('BM' and the offset to the pixels), a DIB header (40 bytes, or 108 and 124 bytes in the V4 and V5 versions that add colour masks and alpha), an optional palette, then pixel rows padded to 4 bytes and normally stored bottom-up.

BMP files usually come from Windows Paint, legacy Windows programs, embedded displays and some scanners.

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 BMP 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.