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73 lines
3.9 KiB
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73 lines
3.9 KiB
HTML
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<h1>MakerNote Formats and Specifications</h1>
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<p>
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The Makernote is tag 0x927c in the Exif IFD. According to the
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<a title="The Exif 2.2 standard (PDF)" href="http://tsc.jeita.or.jp/avs/data/cp3451.pdf">
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Exif 2.2 standard</a>, the makernote is <i>"a tag for manufacturers of
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Exif writers to record any desired information. The contents are up to
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the manufacturer, but this tag should not be used for any other than
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its intended purpose."</i></p>
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<p>Unfortunately, most vendors do not publish their makernote specifications. (Why not?)
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Most of the <a href="#R0">specifications available on the Internet</a>
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were reverse-engineered. Judging from the size of many makernote fields, manufacturers
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apparently store a lot of information there and from the available specifications,
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some of this is certainly quite interesting. For example, makernotes may contain
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information about the lens used, contrast, saturation and sharpness settings, image
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quality settings, etc.</p>
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<p>Many (but not all) vendors write the makernote in TIFF IFD (Image File Directory) format,
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i.e., in the same format as the rest of the Exif information is encoded. Although this may
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appear to make sense at first glance, it actually complicates the situation for programs that
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attempt to write to the Exif data. The problem is that IFDs contain offsets relative to the
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start of the Exif data. That implies that if an Exif writer moves a makernote field encoded in
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IFD format to a different location within the Exif data, it gets corrupted. The reason to
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write to the Exif data could be as simple as to add copyright information, an Exif comment,
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etc. In my opinion, this is a bug in the specification. In fact, some vendors seem to have
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recognized this problem and use offsets relative to somewhere at the beginning of the makernote
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field for the makernote IFD.</p>
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<p>The following table summarizes the structures of the makernote field used by some vendors.
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Please let me know if you find further specifications on the Internet.</p>
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__makernotes__
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<p><a href="http://www.exif.org/">Exif.org</a> has another table with similar
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info and sample pictures: <a href="http://www.exif.org/samples.html">Digital
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Camera Sample Images</a>. According to this source, (at least some) Ricoh and
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Kodak cameras do not write the makernote in IFD format.</p>
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<h2><a name="R0">References</a></h2>
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<p><a name="R1">[1]</a> <a href="http://park2.wakwak.com/%7Etsuruzoh/Computer/Digicams/exif-e.html">Exif
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file format</a> by TsuruZoh Tachibanaya<br>
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<a name="R2">[2]</a> <a href="http://www.burren.cx/david/canon.html">EXIF Makernote
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of Canon</a> by David Burren<br>
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<a name="R3">[3]</a> <a href="http://www.tawbaware.com/990exif.htm">Makernote
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EXIF Tag of the Nikon 990</a> by Max Lyons<br>
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<a name="R4">[4]</a> <a href="http://www.dicasoft.de/casiomn.htm">"Makernote"
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Exif tag of Casio</a> by Eckhard Henkel<br>
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<a name="R5">[5]</a> <a href="http://www.dalibor.cz/minolta/makernote.htm">Minolta
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MakerNote</a> by Dalibor Jelinek<br>
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<a name="R6">[6]</a> <a href="http://www.exif.org/makernotes/SanyoMakerNote.html">Sanyo
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MakerNote</a> by John Hawkins<br>
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<a name="R7">[7]</a> <a href="http://www.x3f.info/technotes/FileDocs/MakerNoteDoc.html">
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SIGMA and FOVEON EXIF MakerNote Documentation</a> by Foveon<br>
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<a name="R8">[8]</a> <a href="http://www.compton.nu/panasonic.html">Panasonic
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MakerNote Information</a> by Tom Hughes<br>
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<a name="R9">[9]</a> <a href="http://www.ozhiker.com/electronics/pjmt/jpeg_info/makernotes.html">
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Various Makernote specifications</a> from the <a href="http://www.ozhiker.com/electronics/pjmt/index.html">
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PHP JPEG Metadata Toolkit</a> by Evan Hunter<br>
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<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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