MakerNote — the vendor's secret section inside EXIF

EXIF tag 0x927C is called MakerNote. The specification reserves it as a binary blob of arbitrary length and structure, controlled entirely by the camera vendor. Every major manufacturer fills it with their own private set of fields — shutter count, AF point selection, in-camera processing decisions, lens information beyond what fits in the standard tags. None of it is documented by the vendors; everything we know about MakerNote schemas comes from years of reverse engineering by the open-source metadata community.

Why it's private

The original 1995 EXIF spec needed to leave room for vendor-specific data without enumerating every camera feature ever invented. Tag 0x927C was the answer: a typed-but-opaque blob. In practice each vendor reused TIFF IFD layout inside, but with their own tag numbers and their own type quirks. Reading a Canon MakerNote with Nikon's schema produces garbage; the parser has to dispatch on the Make tag in the parent IFD before walking inside.

Canon — the most readable

Canon's MakerNote follows TIFF IFD conventions almost cleanly. Field tags are documented (community-maintained tables list 200+ entries). Notable: ShutterCount on supported bodies (a wear meter for used-camera buyers), InternalSerialNumber (factory-burned, distinct from the user-visible BodySerialNumber and harder to spoof), FileNumber (the camera's internal counter, often revealing total photos taken), CustomFunctions (every menu setting the photographer changed from defaults).

Nikon — the encrypted blob

Nikon encrypts portions of its MakerNote. The cipher is a simple XOR-stream with a key derived from the camera's serial number and shutter count, both of which are also stored in the same MakerNote. Once the open-source community figured this out (around 2005), parsers could decrypt the lens model, focal-length-at-capture, and other fields. Not "encryption" in any security sense — it's obfuscation that delays reverse engineering by months, not years.

Sony and others

Sony stores focus mode, scene mode, panorama metadata, and per-shot quality settings. Fujifilm stores film simulation choice and dynamic-range expansion settings. Panasonic and OM Digital follow the TIFF-IFD-inside-blob pattern. Each has roughly 50–200 known fields plus an unknown tail of undocumented bytes.

Apple — the modern one

The Apple MakerNote grew quickly across iOS versions. Notable fields: HDRImageType (which HDR pipeline produced this frame), LivePhotoVideoIndex (linkage to the .MOV companion file in a Live Photo), ContentIdentifier (the UUID that pairs the still and the video — survives sharing if the receiver imports both files), AccelerationVector (the 3-axis accelerometer reading at the moment of capture; can reveal which way the phone was tilted). New iOS releases routinely add new fields.

How our viewer handles it

The bundled ExifTool ships decoded schemas for every major MakerNote dialect (Canon, Nikon, Sony, Olympus, Panasonic, Fujifilm, Apple, and many more), so recognised fields appear in the viewer's tag table with their proper names — Apple:HDRImageType, Canon:ShutterCount, etc. Unrecognised tags within a known vendor show up as Tag_0x#### entries with their raw value. The MakerNote contents are typically more revealing than the standard EXIF — which is exactly why people who care about privacy strip them.