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<h1>MakerNote Formats and Specifications</h1>

<p>
The Makernote is tag 0x927c in the Exif IFD. According to the 
<a title="The Exif 2.2 standard (PDF)" href="http://www.exif.org/Exif2-2.PDF">
Exif 2.2 standard</a>, the makernote is <i>"a tag for manufacturers of
Exif writers to record any desired information. The contents are up to
the manufacturer, but this tag should not be used for any other than
its intended purpose."</i></p> 

<p>Most vendors do not publish their makernote specifications. Most of the 
<a href="#R0">specifications available on the Internet</a> 
were reverse-engineered. Judging from the size of many makernote
fields, manufacturers store a lot of information there and from the
available specifications, some of this is certainly quite
interesting. For example, makernotes may contain information about the
lens used, contrast, saturation and sharpness settings, image quality
settings, etc. For some more advanced camera settings, the Exif
standard doesn't define a standard tag, so camera vendors have to
resort to using the makernote. Unfortunately, in some cases, camera
vendors store important information only in proprietary makernote
fields, instead of using available Exif standard tags. The most
infamous example for this is Nikon's ISO settings tag.</p>

<p>Most vendors write the makernote in TIFF format, i.e., in the same
format as the rest of the Exif information is encoded. This appears to
be a sensible thing at first glance. Unfortunately, in general it
means that <i>any</i> change of an Exif tag, which moves the
makernote field, will corrupt it. It is an inherent problem of the
TIFF format that a writer must know the format and all extensions
used, in order to be able to write changes correctly; unknown tags are
potentially corrupted when they are moved (rearranged). But since
makernotes are usually proprietary, Exif writers often don't know
these details. The reason to write to the Exif data could be as simple
as to add copyright information, an Exif comment, etc. Some camera
manufacturers seem to have recognized this problem and now use a
modified TIFF format with offsets relative to somewhere at the
beginning of the makernote field for the makernote IFD to address the
issue.</p>

<p>The following table summarizes the structures of the makernote
field used by some vendors.  Please let me know if you have additional
information.</p>

__makernotes__

<p><a href="http://www.exif.org/">Exif.org</a> has another table with similar 
  info and sample pictures: <a href="http://www.exif.org/samples.html">Digital 
  Camera Sample Images</a>. According to this source, (at least some) Ricoh and 
  Kodak cameras do not write the makernote in IFD format.</p>
<h2><a name="R0">References</a></h2>
<p><a name="R1">[1]</a> <a href="http://park2.wakwak.com/%7Etsuruzoh/Computer/Digicams/exif-e.html">Exif 
  file format</a> by TsuruZoh Tachibanaya<br>
  <a name="R2">[2]</a> <a href="http://www.burren.cx/david/canon.html">EXIF Makernote 
  of Canon</a> by David Burren<br>
  <a name="R3">[3]</a> <a href="http://www.tawbaware.com/990exif.htm">Makernote 
  EXIF Tag of the Nikon 990</a> by Max Lyons<br>
  <a name="R4">[4]</a> <a href="http://www.dicasoft.de/casiomn.htm">&quot;Makernote&quot; 
  Exif tag of Casio</a> by Eckhard Henkel<br>
  <a name="R5">[5]</a> <a href="http://www.dalibor.cz/minolta/makernote.htm">Minolta 
  MakerNote</a> by Dalibor Jelinek<br>
  <a name="R6">[6]</a> <a href="http://www.exif.org/makernotes/SanyoMakerNote.html">Sanyo 
  MakerNote</a> by John Hawkins<br>
  <a name="R7">[7]</a> <a href="http://www.x3f.info/technotes/FileDocs/MakerNoteDoc.html">
  SIGMA and FOVEON EXIF MakerNote Documentation</a> by Foveon<br>
  <a name="R8">[8]</a> <a href="http://www.compton.nu/panasonic.html">Panasonic 
  MakerNote Information</a> by Tom Hughes<br>
  <a name="R9">[9]</a> <a href="http://www.ozhiker.com/electronics/pjmt/jpeg_info/makernotes.html">
  Various Makernote specifications</a> from the <a href="http://www.ozhiker.com/electronics/pjmt/index.html">
  PHP JPEG Metadata Toolkit</a> by Evan Hunter<br>
  <a name="R10">[10]</a> <a href="http://www.sno.phy.queensu.ca/~phil/exiftool/">ExifTool</a>, the most complete and up-to-date tool for reading and writing meta information in image files, by Phil Harvey</p>

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