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<div class='index'>
<ol class='index'>
<li><a href="#Q1">Discussion forum</a></li>
<li><a href="#Q2">Determining tag names</a></li>
<li><a href="#Q3">Problems with duplicate tags</a></li>
<li><a href="#Q4">Aperture and shutter speed</a></li>
<li><a href="#Q5">Date and time formats</a></li>
<li><a href="#Q6">"Can't convert TAG" errors</a></li>
<li><a href="#Q7">Deleting all EXIF from a TIFF</a></li>
<li><a href="#Q8">Writing Make, Model & MakerNotes</a></li>
<li><a href="#Q9">Tag locations when copying</a></li>
<li><a href="#Q10">Coded character sets</a></li>
<li><a href="#Q11">User-defined tags</a></li>
<li><a href="#Q12">Export to database</a></li>
<li><a href="#Q13">Output file size</a></li>
<li><a href="#Q14">GPS coordinate format</a></li>
<li><a href="#Q15">MakerNote errors</a></li>
<li><a href="#Q16">Some files not renamed</a></li>
<li><a href="#Q17">List-type tags</a></li>
<li><a href="#Q18">Windows character encoding</a></li>
<li><a href="#Q19">Formatting tag values</a></li>
<li><a href="#Q20">Write errors (repair corrupted EXIF)</a></li>
</ol>
</div>
<h1 class='up'>ExifTool FAQ</h1>
<a name="Q1"></a>
<p>1. <b>"Is there a forum for discussing ExifTool issues?"</b></p>
<blockquote>
ExifTool issues can be discussed on the CPAN forum at
<a href="http://www.cpanforum.com/dist/Image-ExifTool">http://www.cpanforum.com/dist/Image-ExifTool</a>
</blockquote>
<a name="Q2"></a>
<p>2. <b>"How do I determine the tag name for some information?"</b></p>
<blockquote>
When you run exiftool, by default it prints descriptions, not tag names, for
the information it extracts. To print the tag names instead, use the
<code>-s</code> option. Also, see the <a href="TagNames/index.html">tag names
documentation</a> for a complete list of available tag names.</blockquote>
<blockquote>Tag names may be optionally prefixed by a family 0 or 1 group name
to specify a particular information type or location. Use the
<code>-g0</code> and <code>-g1</code> (or
<code>-G0</code> and <code>-G1</code>) options when extracting
information to see the corresponding group names.
</blockquote>
<a name="Q3"></a>
<p>3a. <b>"ExifTool reports the wrong value or doesn't extract a tag"</b>,
<br>3b. <b>"ExifTool doesn't write a tag properly"</b>, or
<br>3c. <b>"Other software can't read information written by ExifTool"</b></p>
<blockquote>
Make sure you are looking at the right information. Information may be
duplicated in different locations within an image. When in doubt, use
"<code>exiftool -a -G1 FILENAME</code>" to show all information and the
locations in the file. In this command, <code>-a</code> allows
duplicate tags to be extracted, <code>-G1</code> shows the family 1
group name (ie. the location) of each tag, and "<code>FILENAME</code>" is
the name of your image file. Also, it may be helpful to add
<code>-s</code> to show the actual tag names instead of the
descriptions (and possibly <code>-D</code> or <code>-H</code> to
show the tag ID numbers if you are familiar with these).</blockquote>
<blockquote>When duplicate tags exist, only one is extracted unless the
<code>-a</code> option is used. Beware that options like <code>-EXIF:all</code>
select all EXIF tags from the extracted tags, so EXIF tags hidden by duplicate
tags in other locations will not appear in the output for
<code>-EXIF:all</code>. For example, the command
<pre>exiftool -gps:all image.jpg</pre>
will NOT necessarily extract all GPS tags because some GPS tags may have been
suppressed by same-named tags in other groups. To be sure all GPS tags are
extracted, the <code>-a</code> option must be used:
<pre>exiftool -a -gps:all image.jpg</pre>
If you are having problems with other software reading information written by
ExifTool, if possible try first writing the information from the other software,
then use ExifTool to determine where the information was written. Once you know
where it should go, you can use ExifTool to write to this location.</blockquote>
<blockquote>You can read or write information in a specific location by
prefixing the tag name on the command line with the desired group name. ie)
"<code>-ExifIFD:DateTimeOriginal</code>"
</blockquote>
<a name="Q4"></a>
<p>4. <b>"ExifTool reports more than one shutter speed or aperture value, and
they are slightly different"</b></p>
<blockquote>
There are a number of different ways that aperture and shutter speed information
are stored in many images. The standard EXIF values (EXIF:FNumber and
EXIF:ExposureTime) should correspond to the values displayed by your camera,
but these values may have been rounded off. The corresponding EXIF APEX
values (EXIF:ApertureValue and EXIF:ShutterSpeedValue) may be different due
to their own round-off errors. If available, the MakerNotes values may be
the most accurate because they haven't been rounded off to nice even values
for display, so with these you may see odd values like 1/102 instead of
1/100, etc.
</blockquote>
<a name="Q5"></a>
<p>5. <b>"How do I format date and time information for writing?"</b></p>
<blockquote>All information (including date/time information) is written in the
same format as it is read out. When reading, ExifTool converts all date and
time information to standard EXIF format, so this is also the way it is
specified when writing. The standard EXIF date/time format is "<code>YYYY:MM:DD
hh:mm:ss</code>", and some meta information formats such as XMP also allow
sub-seconds and a timezone to be specified. The timezone format is
"<code>+hh:mm</code>", "<code>-hh:mm</code>" or "<code>Z</code>". For
example:
<pre>exiftool -xmp:dateTimeOriginal="2005:10:23 20:06:34.33-05:00" a.jpg
</pre>
When writing XMP or other information types which allow incomplete date/time
values, the following input formats are also accepted:
<pre>YYYY
YYYY:MM
YYYY:MM:DD
YYYY:MM:DD hh:mm
</pre>
ExifTool will attempt to reformat input date/time values into the standard
format unless the <code>-n</code> option is used.
</blockquote>
<a name="Q6"></a>
<p>6. <b>"I get '<code>Can't convert TAG (not in PrintConv)</code>' errors when
writing a tag"</b></p>
<blockquote>
By default, ExifTool applies a print conversion (PrintConv) to extracted
information to make the output more human-readable. Some conversions involve
lookup tables which are documented in the <b>Values</b> column of the
<a href="TagNames/index.html">Tag Name documentation</a>. For example, the
GPSAltitudeRef tag defines the following conversions:
<pre>0 = Above Sea Level
1 = Below Sea Level
</pre>
For this tag, a value of '0' is printed as 'Above Sea Level', and '1' is printed
as 'Below Sea Level'. Reading and writing with ExifTool is symmetrical <i>[with
the possible exception of List-type tags -- see <a href="#Q17">FAQ #17</a>
below]</i>, so a value that is printed as 'Above Sea Level' must also be written in
that form. (ie. The inverse print conversion is applied when writing values.)
For example, to write GPSAltitudeRef you can type:
<pre>exiftool -gpsaltituderef="Above Sea Level" image.jpg
</pre>
or any unambiguous short form may be used and ExifTool will know what you mean, ie)
<pre>exiftool -gpsaltituderef=above image.jpg
</pre>
Alternatively, the print conversion can be disabled for all tags with the
<code>-n</code> option, or for individual tags by suffixing the tag name with a
'<code>#</code>' character. In either case the printed value of GPSAltitudeRef
will be '0' or '1' when extracting information, and the value is written in the
same way. So following two commands have exactly the same effect as above:
<pre>exiftool -gpsaltituderef=0 -n image.jpg
exiftool -gpsaltituderef#=0 image.jpg
</pre>
Integer values may also be specified in hexadecimal (with a leading '0x'). For
example, the following commands are all valid and accomplish the same thing:
<pre>exiftool -flash=1 -n image.jpg
exiftool -flash=0x1 -n image.jpg
exiftool -flash#=1 image.jpg
exiftool -flash#=0x1 image.jpg
exiftool -flash=fired image.jpg
</pre>
Programmers: These techniques look like this when calling Image::ExifTool
functions from a Perl script:
<pre>$exifTool->SetNewValue(GPSAltitudeRef => 'Above Sea Level');
$exifTool->SetNewValue(GPSAltitudeRef => 0, Type => 'ValueConv');
$exifTool->SetNewValue('GPSAltitudeRef#' => 0);
</pre>
</blockquote>
<a name="Q7"></a>
<p>7. <b>"I can't delete all EXIF information from a TIFF file using
'<code>exiftool -exif:all= img.tif</code>'"</b></p>
<blockquote>
This is because of the way a TIFF file is structured. With a JPEG image, this
command will remove IFD0 (the main Image File Directory) as well as any
subdirectories, thus removing all EXIF information. But with the TIFF format,
the main image itself is stored in IFD0, so deleting this directory would
destroy the image. Instead, ExifTool just deletes the ExifIFD subdirectory, and
any information stored in other directories is preserved.</blockquote>
<blockquote>Use "<code>exiftool -a -G1 -s img.tif</code>" to
see where the information is stored. Any information remaining in other IFD's
must be deleted separately from a TIFF file if desired.
</blockquote>
<a name="Q8"></a>
<p>8a. <b>"All maker note information is lost if I change the Make or Model tag"</b>, or
<br>8b. <b>"I can't copy maker note information to an image"</b></p>
<blockquote>
The Make and Model tags are used by some image utilities (including ExifTool) to
determine the format of the maker note information. Deleting or changing either
of these tags may prevent these utilities from recognizing or properly
interpreting the maker notes. Also beware that the maker notes information may
be damaged if an image is edited when the maker notes are not properly
recognized. So it is a good idea not to edit the Make and Model tags in the
first place.</blockquote>
<blockquote>If you really want to delete the Make and Model information, you
might as well delete the maker notes too. You can do this with either of the
following commands:
<pre>exiftool -make= -model= -makernotes:all= image.jpg
exiftool -make= -model= -makernotes= image.jpg
</pre>
For the same reason, maker notes can not be copied to an image with an
incompatible Make or Model. To do this, the Make and Model tags must also be
copied. ie)
<pre>exiftool -tagsfromfile src.jpg -makernotes -make -model dst.jpg
</pre>
(Note that in this case the "<code>-makernotes:all</code>" syntax does not
work because it attempts to copy the maker note tags individually, but they
must be copied as a block with "<code>-makernotes</code>".)
</blockquote>
<a name="Q9"></a>
<p>9a. <b>"The information is different when I copy all tags to a new file"</b>, or
<br>9b. <b>"The tag locations change when I use <code>-tagsfromfile</code>
to copy information"</b></p>
<blockquote>
This feature is explained under the <code>-tagsFromFile</code> option in
the <a href="exiftool_pod.html">exiftool application documentation</a>, but the
question is common enough that it is discussed here in more detail.</blockquote>
<blockquote>By default, ExifTool will store information in preferred locations
when either writing new information or copying information between files. This
freedom allows ExifTool to write or copy information to files of different
formats without requiring the user to know details about where the information
is stored.</blockquote>
<blockquote>The preferred locations for information written to JPEG images are
1) EXIF, 2) IPTC and 3) XMP. As an example, information extracted from the
maker notes will be preferentially written (on a tag-by-tag basis) in EXIF
format when copying information between two JPEG images. But if a specific tag
doesn't exist in EXIF, then the tag is written to the first valid group in the
order specified above. The advantage of "translating" the information to EXIF
is that it then becomes readable by applications which only support standard
EXIF. The disadvantage is that you don't get an exact copy of the original
information structure.</blockquote>
<blockquote>But ExifTool gives you the ability to customize this behaviour to
write the information to wherever you want. This is done by specifying a group
name for the tag(s) to be copied. This applies even if the group name is
"<code>all</code>", in which case the original group is preserved. So to copy
all information and preserve the original structure, use this syntax:
<pre>exiftool -tagsfromfile src.jpg -all:all dst.jpg
</pre>
By specifying a group name with "<code>-all:all</code>", the location of the
information is preserved. (Specifically, since no destination tag was
specified the source group "<code>all</code>" was assumed, thus preserving
the original group.)</blockquote>
<blockquote>Here are some examples to show you the type of control you have over
where the information is written. All commands in each example are equivalent:
<pre><span class='blk'># copy all tags to preferred groups (no destination group)</span>
exiftool -tagsfromfile src.jpg dst.jpg
exiftool -tagsfromfile src.jpg -all dst.jpg
exiftool -tagsfromfile src.jpg "-all>all" dst.jpg
exiftool -tagsfromfile src.jpg "-all:all>all" dst.jpg
<span class='blk'># copy all tags, preserving original group (destination group 'all')</span>
exiftool -tagsfromfile src.jpg -all:all dst.jpg
exiftool -tagsfromfile src.jpg "-all>all:all" dst.jpg
exiftool -tagsfromfile src.jpg "-all:all>all:all" dst.jpg
<span class='blk'># copy all tags to EXIF group only (destination group 'exif')</span>
exiftool -tagsfromfile src.jpg "-all>exif:all" dst.jpg
exiftool -tagsfromfile src.jpg "-all:all>exif:all" dst.jpg
<span class='blk'># copy XMP tags to XMP group (destination group 'xmp' or 'all')</span>
exiftool -tagsfromfile src.jpg "-xmp:all" dst.jpg
exiftool -tagsfromfile src.jpg "-xmp:all>xmp:all" dst.jpg
exiftool -tagsfromfile src.jpg "-xmp:all>all:all" dst.jpg
<span class='blk'># copy XMP tags to preferred groups (no destination group)</span>
exiftool -tagsfromfile src.jpg "-xmp:all>all" dst.jpg
<span class='blk'># copy XMP tags to EXIF only (destination group 'exif')</span>
exiftool -tagsfromfile src.jpg "-xmp:all>exif:all" dst.jpg
</pre>
The same rules illustrated above also apply when copying individual tags.</blockquote>
<blockquote>Note: If no destination group is specified, a new tag is created if
necessary only in the preferred group, but if the same tag already exists in
another group, then this information is also updated. (Otherwise inconsistent
values for the same information would exist in different locations. Of course,
you can always generate inconsistencies like this if you really want to by
specifically writing contradictory information to different groups.)
</blockquote>
<a name="Q10"></a>
<p>10. <b>"How does ExifTool handle coded character sets?"</b></p>
<blockquote><i>[Also see <a href="#Q18">FAQ number 18</a> for help on displaying
special characters in a Windows console.]</i></blockquote>
<blockquote>
Certain meta information formats allow coded character sets other than plain
ASCII. When reading, 8‑bit encodings are passed straight through ExifTool
without translation (unless specified otherwise below), and multi-byte encodings
are translated according to the exiftool <code>-charset</code> option, or to
UTF‑8 by default. The <code>-L</code> option is equivalent to
"<code>-charset Latin</code>", "<code>-charset Latin1</code>" and
"<code>-charset cp1252</code>". When writing, the inverse translations are
performed. Alternatively, special characters may be translated to/from HTML
character entities when reading/writing with the <code>-E</code> option.
</blockquote>
<blockquote>Valid <code>-charset</code> values are (with aliases given in
brackets):
<blockquote><table class=clear>
<tr><td>UTF8</td><td>(cp65001, UTF-8)</td><td>Thai</td><td>(cp874)</td></tr>
<tr><td>Latin</td><td>(cp1252, Latin1)</td><td>MacRoman</td><td>(cp10000, Mac, Roman)</td></tr>
<tr><td>Latin2</td><td>(cp1250)</td><td>MacLatin2</td><td>(cp10029)</td></tr>
<tr><td>Cyrillic</td><td>(cp1251, Russian) </td><td>MacCyrillic</td><td>(cp10007)</td></tr>
<tr><td>Greek</td><td>(cp1253)</td><td>MacGreek</td><td>(cp10006)</td></tr>
<tr><td>Turkish</td><td>(cp1254)</td><td>MacTurkish</td><td>(cp10081)</td></tr>
<tr><td>Hebrew</td><td>(cp1255)</td><td>MacRomanian</td><td>(cp10010)</td></tr>
<tr><td>Arabic</td><td>(cp1256)</td><td>MacIceland</td><td>(cp10079)</td></tr>
<tr><td>Baltic</td><td>(cp1257)</td><td>MacCroatian</td><td>(cp10082)</td></tr>
<tr><td>Vietnam</td><td>(cp1258)</td></tr>
</table></blockquote>
More specific details are given below about how character coding is
handled for EXIF, IPTC, XMP, ID3, PDF and MIE information:</blockquote>
<blockquote><b>EXIF</b>: Most textual information in EXIF is stored in ASCII
format, and ExifTool does not translate these tags. However it is not uncommon
for applications to write UTF-8 or other encodings where ASCII is expected, and
ExifTool will quite happily read/write any encoding without translation. For a
few EXIF tags (UserComment, GPSProcessingMethod and GPSAreaInformation) the
stored text may be encoded either in ASCII, Unicode (UCS-2) or JIS. When reading
these tags, Unicode and JIS are translated to the character set specified by
the <code>-charset</code> or <code>-L</code> option, or to UTF‑8 by
default. Other encodings are not translated. When writing, text is stored as
ASCII unless the string contains special characters, in which case it is
translated from the specified character set and stored as Unicode. ExifTool
writes Unicode in native EXIF byte ordering by default, but this may be changed
by setting the ExifUnicodeByteOrder tag (see the <a href="TagNames/Extra.html">Extra
Tags</a> documentation). The EXIF "XP" tags (XPTitle, XPComment, etc) are
always stored as little-endian Unicode, and are read and written using the
specified character set.</blockquote>
<blockquote><b>IPTC</b>: The value of the IPTC:CodedCharacterSet tag determines
how the internal IPTC string values are interpreted. If CodedCharacterSet
exists and has a value of "<code>UTF8</code>" (or
"<code>ESC % G</code>") then string values are assumed to be stored as
UTF‑8, otherwise Windows Latin1 (cp1252) coding is assumed by default, but
this can be changed with "<code>-charset iptc=CHARSET</code>". When reading,
these strings are translated to UTF‑8 by default, or to the character set
specified by the <code>-charset</code> or <code>-L</code> option. When writing,
the inverse translations are performed. No translation is done if the internal
(IPTC) and external (ExifTool) character sets are the same. Note that ISO 2022
character set shifting is not supported. Instead, a warning is issued and the
string is not translated if an ISO 2022 shift code is found. See the <a
href="http://www.iptc.org/IIM/">IPTC specification</a> for more information
about IPTC character coding.</blockquote>
<blockquote>ExifTool may be used to convert IPTC values to a different internal
encoding. To do this, all IPTC tags must be rewritten along with the desired
value of CodedCharacterSet. For example, the following command changes the
internal IPTC encoding to UTF‑8:
<pre>exiftool -tagsfromfile @ -iptc:all -codedcharacterset=utf8 a.jpg
</pre>and this command changes it back from UTF‑8 to Windows Latin1 (cp1252):
<pre>exiftool -tagsfromfile @ -iptc:all -codedcharacterset= a.jpg
</pre>or this command changes it back from UTF‑8 to Windows Latin2 (cp1250):
<pre>exiftool -tagsfromfile @ -iptc:all -codedcharacterset= -charset iptc=latin2 a.jpg
</pre>But note that unless UTF‑8 is used, applications have no reliable
way to determine the IPTC character encoding.</blockquote>
<blockquote><b>XMP</b>: Exiftool reads XMP encoded as UTF‑8, UTF‑16
or UTF‑32, and converts them all to UTF‑8 internally. Also, all XML
character entity references and numeric character references are converted.
When writing, ExifTool always encodes XMP as UTF‑8, converting the
following 5 characters to XML character references: <code>& < > '
"</code>. By default no further translation is performed, however the
<code>-charset</code> or <code>-L</code> option may be used used to translate
text to/from a specified character set when reading/writing.</blockquote>
<blockquote><b>ID3</b>: The ID3v1 specification officially supports only ISO
8859‑1 encoding (a subset of Windows Latin1), although some applications
may incorrectly use other character sets. By default ExifTool translates ID3v1
text from Latin to the character set specified by the <code>-charset</code> or
<code>-L</code> option, or to UTF‑8 by default. However, the internal
ID3v1 charset may be specified with "<code>-charset id3=CHARSET</code>". The
encoding for ID3v2 information is stored in the file, so ExifTool translates
ID3v2 text from this encoding to the character set specified by
<code>-charset</code> or <code>-L</code>, or to UTF‑8 by default. ExifTool
does not currently write ID3 information.</blockquote>
<blockquote><b>PDF</b>: PDF text strings are stored in either PDFDocEncoding
(similar to Windows Latin1) or Unicode (UCS‑2). When reading, ExifTool
translates to the character set specified by the <code>-charset</code> or
<code>-L</code> option, or to UTF‑8 by default. When writing, exiftool
encodes input text from the specified character set as Unicode only if the
string contains special characters, otherwise PDFDocEncoding is
used.</blockquote>
<blockquote><b>MIE</b>: MIE strings are stored as either UTF‑8 or ISO
8859‑1. When reading, UTF‑8 strings are translated according to
the <code>-charset</code> or <code>-L</code> option, and ISO 8859‑1
strings are never translated. When writing, input strings are translated from
the specified character set to UTF‑8. The resulting strings are stored as
UTF‑8 if they contain multi-byte UTF‑8 character sequences,
otherwise they are stored as ISO 8859‑1.</blockquote>
<a name="Q11"></a>
<p>11. <b>"My user-defined tags don't work"</b></p>
<blockquote>
For examples of how to add user-defined tags, see the
<a href="config.html">ExifTool_config</a> file in the ExifTool distribution. To
activate this file, rename it to "<code>.ExifTool_config</code>" and copy it to
your <b>HOME</b> directory. (Windows users must rename the file using the
"<code>rename</code>" command in a cmd shell because the Windows GUI won't let
you use a file name beginning with a "<code>.</code>".) With this installed,
you should be able to write and read the example tags (such as
"<code>NewXMPxxxTag1</code>"). Try this first before you attempt to define your
own tags.</blockquote>
<blockquote>If this doesn't work, the most common problem is that the
"<code>.ExifTool_config</code>" configuration file isn't getting loaded
properly, and there are a few things you can try which may help with this:
<ol><li>Set either the <b>HOME</b> or the <b>EXIFTOOL_HOME</b> environment
variable to the name of the directory where you put your
"<code>.ExifTool_config</code>" file</li>
<li>Put the config file in the same
directory as the exiftool script. (Also, be sure the config filename starts
with a dot! In the Windows GUI you may be not be able to generate a file name
that starts with a '<code>.</code>', but it can be done from the command line
using the '<code>rename</code>' command.)</li>
<li>If running on a system with case-sensitive filenames (ie. Linux), check the
case of your config file. It must be "<code>.ExifTool_config</code>" (note
the capital "<code>T</code>").</li>
<li>Use the <code>-config <i>CFGFILE</i></code> option to load the config file
by name. (If used, this must be the first option on the command line.)</li>
</ol>
</blockquote>
<blockquote>If necessary, you can verify that ExifTool is loading your config
file by adding the following line to your file:
<pre>print "LOADED!\n";
</pre>
If you see a "<code>LOADED!</code>" message when you run exiftool, but your new
tags still don't work, make sure you are using the proper tag name and that the
file you are writing can support these names. Try copying the
"<code>t/images/Writer.jpg</code>" file from the distribution and running
exiftool with the following command:
<pre>exiftool -v2 -NewXMPxxxTag1=test Writer.jpg
</pre>
If ExifTool recognizes the new tag, the first line of output from this command
should be
<pre>"Writing XMP-xxx:NewXMPxxxTag1"
</pre>
Then you can read back the new tag with "<code>exiftool -s Writer.jpg</code>".
</blockquote>
<blockquote>To specify the config file directory from within a Perl script when
using the ExifTool API, set the <b>EXIFTOOL_HOME</b> environment variable before
loading the ExifTool module:
<pre>BEGIN { $ENV{EXIFTOOL_HOME} = '/config_file_directory' }
use Image::ExifTool;
</pre></blockquote>
<a name="Q12"></a>
<p>12. <b>"How do I export information from exiftool to a database?"</b></p>
<blockquote>
It is often easiest to export information formatted as a tab-delimited list of
values. The following exiftool options may be useful for this purpose:
<pre>-t - use a tab instead of spaces to separate output values
-S - very short format (with -t, prints only tag values)
-q - quiet (suppresses any other messages)
-f - force '-' to be printed for non-existent values
-T - shortcut for the combination of all above options (-t -S -q -f)
-r - recursively process files in subdirectories
</pre>
And here is an example command line:
<pre>exiftool -T -r -filename -aperture -ISO t/images > out.txt
</pre></blockquote>
<blockquote>This command recursively processes all images in the
"<code>t/images</code>" directory, extracting FileName, Aperture and ISO tags,
and writing the output to a file called "<code>out.txt</code>". After the
command has executed, the output file will contain information in the following
format:
<pre>Canon.jpg 14.0 100
Casio.jpg 2.0 -
Nikon.nef 3.5 200
OlympusE1.jpg 4.5 400
</pre>
It should be possible to import a file like this directly into most database
applications. On the command line, any list of tag names may be used, and
any number of file or directory names may be specified. (Hint: If your
command line starts to get too long, you may want to look into using the
<code>-@</code> option and/or the <a href="index.html#shortcut">ShortCut</a>
feature).
</blockquote>
<blockquote>Another approach is to export information in RDF/XML format using
the <code>-X</code> option, or JSON (JavaScript Object Notation) using the
<code>-j</code> option. These methods allow transfer of more complex data
sets, but require that the importing software supports these formats.
</blockquote>
<a name="Q13"></a>
<p>13. <b>"Why is my file smaller after I use ExifTool to write information?"</b></p>
<blockquote>
There are various specific reasons why this can happen, but the general answer
is: When ExifTool writes an image, the meta information may be restructured in
such a way that it takes less space than in the original file.</blockquote>
<blockquote>For instance, the EXIF/TIFF standard allows for blocks of
unreferenced data to exist in an image. Some digital cameras write JPEG or
TIFF-based RAW files which contain large blocks of unused data, usually filled
with binary zeros. The reason for this could be to simplify camera algorithms
by allowing variable-sized information to be written at fixed offsets in the
output image. When ExifTool rewrites an image it does not copy these unused
blocks. This can result in a significant reduction in file size for some
images. <i>[The <code>-htmlDump</code> option may be used to view the file
structure if you are interested in seeing these unused data blocks -- use a
command like "<code>exiftool -htmlDump a.jpg > out.html</code>", then open the
output HTML file with your web browser.]</i>
</blockquote>
<blockquote>Also, the size of an XMP record may easily shrink or grow when it is
rewritten, even if no meta information is changed. This is partly due to the
fact that the XMP specification recommends a few KB of padding at the end of the
record (ExifTool adds 2424 bytes by default), and partly due to the flexibility
of the XMP format which allows the information to be written in various styles,
some of which are more compact than others.
</blockquote>
<blockquote>You may also notice that the values of some "offset" tags (like
ThumbnailOffset and PreviewImageStart) may change when the file is rewritten.
This is normal, and simply indicates that the associated data is now stored at a
different position within the file.</blockquote>
<blockquote>ExifTool does not modify the image data itself, so editing a file is
"lossless" as far as the image is concerned.</blockquote>
<a name="Q14"></a>
<p>14. <b>"What format do I use for writing GPS coordinates?"</b></p>
<blockquote>ExifTool is very flexible in the formats allowed for entering GPS
coordinates. Any string containing between 1 and 3 floating point numbers is
valid. The numbers represent degrees, (and optionally) minutes and
seconds.</blockquote>
<blockquote>For EXIF GPS coordinates, the reference direction is specified
separately with the EXIF:GPSLatitudeRef or EXIF:GPSLongitudeRef
tag.</blockquote>
<blockquote>For XMP GPS coordinates, the reference direction is specified within
the XMP:GPSLatitude or XMP:GPSLongitude value, with west longitudes and south
latitudes being specified either by negative coordinate values or by ending the
string with "<code>W</code>" or "<code>S</code>". </blockquote>
<blockquote>Here are some examples of equivalent ways to specify a GPS
latitude in both EXIF and XMP:
<pre>exiftool -exif:gpslatitude="42 30 0.00" -exif:gpslatituderef=S a.jpg
exiftool -exif:gpslatitude="42 deg 30.00 min" -exif:gpslatituderef=S a.jpg
exiftool -exif:gpslatitude=42.5 -exif:gpslatituderef=S a.jpg
exiftool -xmp:gpslatitude="42 30 0.00 S" a.jpg
exiftool -xmp:gpslatitude=42.50S a.jpg
exiftool -xmp:gpslatitude=-42.5 a.jpg
</pre>
Similar styles may be used for longitude. ExifTool will convert any of these
coordinate styles to the proper format for the specific tag used.
</blockquote>
<a name="Q15"></a>
<p>15. <b>"I get MakerNote warnings or errors when reading or writing information"</b></p>
<blockquote>Problems like this may be caused by image editing software which
doesn't properly update offsets in the MakerNotes when rewriting an image. In
many cases, ExifTool will detect this type of problem and issue a warning like
this:
<pre>Warning: [minor] Possibly incorrect maker notes offsets (fix by -340?)
</pre>
(Be aware that if multiple warnings occur, the <code>-a</code> option must be
used so see them all, since by default only one warning is displayed per file.)
If this warning occurs, you can use the <code>-F</code> option to attempt to fix
the problem. When writing, <code>-F</code> applies a permanent correction to
the maker notes. Note that some Makernote information may be lost permanently
if the proper correction is not applied when writing images with this
problem.</blockquote>
<blockquote>Any error that occurs while writing will prevent the file from being
written. However, most Makernote errors are designated as <b>minor</b>, which
allows them to be ignored by using the <code>-m</code> option. For example:
<pre>Error: [minor] Bad format (65535) for MakerNotes entry 17
</pre>
Using <code>-m</code> will downgrade the minor error to a warning, allowing the
file to be written, but some Makernote information may be lost when ignoring
certain types of errors like this.
</blockquote>
<a name="Q16"></a>
<p>16. <b>"Why doesn't ExifTool rename my AVI files?"</b></p>
<blockquote>By default, ExifTool only processes <u>writable file
types</u><span class='sm'><sup>†</sup></span> when <u>any
tag</u><span class='sm'><sup>‡</sup></span> is being written and a
directory name is specified on the command line. To force exiftool to process
other files, they must either be listed on the command line by name, or be
specified using the <code>-ext</code> option, something like this:
<pre>exiftool -ext AVI -ext JPG -d pics/%Y/%m "-directory<dateTimeOriginal" DIR
</pre>
When a single <code>-ext</code> option is used, only files of the specified type
are processed. However, multiple <code>-ext</code> options may be used in the
same command (as in the example above) to process any number of different file
types.
</blockquote>
<blockquote class='sm'><sup>†</sup>The <code>-listwf</code> option
may be used to list all writable file types.
<br><sup>‡</sup> This includes "pseudo" tags like FileName, Directory and
FileModifyDate.</blockquote>
<a name="Q17"></a>
<p>17. <b>"List-type tags do not behave as expected"</b></p>
<blockquote>Tags indicated by a plus sign (<code>+</code>) in the
<a href="TagNames/index.html">tag name documentation</a> are List-type tags.
Two common examples of List-type tags are
<a href="TagNames/IPTC.html#ApplicationRecord">IPTC:Keywords</a> and
<a href="TagNames/XMP.html#dc">XMP:Subject</a>. These tags may have multiple
values which are combined into a single string when reading. (By default,
extracted values are separated by a comma and a space, but the <code>-sep</code>
option may be used to change this.) When writing, separate
values are always assigned individually, like this:
<pre>exiftool -keywords=one -keywords=two -keywords=three DIR
</pre>
NOT all together, because this would represent a single keyword:
<pre>exiftool -keywords="one, two, three" test.jpg
</pre>
With exiftool version 7.56 or later, the <code>-sep</code> option may be used to
split values of list-type tags into separate items. For example,
<pre>exiftool -sep ", " -keywords="one, two, three" DIR
</pre>
will store three separate keywords, the same as the first example above. This
feature may also be used to split a tag value into separate items if it was
originally stored incorrectly as a single string:
<pre>exiftool -sep ", " -tagsfromfile @ -keywords test.jpg
</pre>
However, sometimes it is desirable to have list items which contain a comma, and
this is allowed:
<pre>exiftool -contributor="Harvey, Phil" -contributor="Marley, Bob" a.jpg
</pre>
But to distinguish these entries when extracting information, a different list
separator must be used. For instance, the following command uses
"<code>//</code>" to separate list items,
<pre>exiftool -contributor -sep "//" a.jpg
</pre>
and produces an output like this:
<pre class=blk>Contributor : Harvey, Phil//Marley, Bob
</pre>
Note that the above examples overwrite any values which already existed in the
original file for these tags. Alternatively, "<code>+=</code>" or
"<code>-=</code> may be used to add to or remove from an existing list:
<pre>exiftool -keywords+="add this" -keywords-="remove this" DIR
</pre>
Using "<code>=</code>" is equivalent to "<code>+=</code>" in any command where
the same tag is set with "<code>+=</code>" or "<code>-=</code>" in another
assignment. (ie. existing values will be preserved unless specifically deleted
with "<code>-=</code>".)
</blockquote>
<blockquote>To prevent duplication when adding new values, specific values can
be deleted then added back again in the same command. For example, the
following command adds the keywords "one" and "two", ensuring that they are not
duplicated if they already existed in the keywords of an image:
<pre>exiftool -keywords-=one -keywords+=one -keywords-=two -keywords+=two DIR
</pre>
When copying list tags using the <code>-tagsFromFile</code> option,
values are copied individually to form proper lists. However, it gets a bit
tricky when copying multiple tags to a single list tag: Here, any assignment to
a tag overrides earlier assignments to the same tag in the command. For
instance, this command
<pre>exiftool "-keywords<filename" "-keywords<comment" DIR
</pre>
writes only the Comment tag. (Note that <code>-tagsFromFile @</code> is implied
by the "<code><</code>" operation in this command, causing tags to be copied
from the original file.) This may seem strange, but it prevents duplicate items
from being added to a list when copying a group of tags from a file containing
duplicate information. If you really want to add values from multiple tags, use
the <code>-addTagsFromFile</code> option instead:
<pre>exiftool -addTagsFromFile @ "-keywords<filename" "-keywords<comment" DIR
</pre>
Note that as with "<code>=</code>" in the first three examples above, the
"<code><</code>" operation of this command overwrites any Keywords that
existed previously in the original file. To add to or remove from the existing
keywords, use "<code>+<</code>" or "<code>-<</code>".
</blockquote>
<a name="Q18"></a>
<p>18. <b>"Special characters don't display properly in my Windows console"</b></p>
<blockquote>The Windows cmd.exe console uses an MS-DOS encoding by default
(cp437 or something similar, depending on your region). The exiftool
<code>-charset</code> option may be used to encodes the exiftool output for a
specific Windows code page, which may help display some special characters, but
instead it may be better to switch the console to UTF‑8 (the native
ExifTool character encoding). This is especially useful if you are using the
<code>-lang</code> option to translate exiftool output to another language. To
change the the Windows console to UTF‑8, follow these steps:
<ol><li>Run "cmd.exe" to open a Windows console (select "Run..." from the
Start menu and enter "cmd").</li>
<li>Change the font in the console Properties to any True Type font (ie. "TT
Lucida Console").</li>
<li>Type "<code>chcp 65001</code>" then press RETURN at the command prompt.</li>
</ol>
The console should now be able to display UTF‑8 characters (cp65001). But
note that the TT Lucida Console font shipped with Windows, at least my version,
may not be very complete, and doesn't seem to contain Japanese or Chinese
characters.</blockquote>
<blockquote>To permanently set the font, select "Save properties for future
windows" when changing the font Properties. Also, you can automatically run
"<code>chcp 65001</code>" every time "cmd.exe" is launched by changing the
Windows Registry for the Command Processor: Run "regedit" and put "<code>chcp
65001</code>" into Data field for "HKEY_LOCAL_MACHINE\Software\Microsoft\Command
Processor\Autorun". (Unfortunately, I haven't been able to figure out how to
change the code page for exiftool when launched via the Windows GUI. If anyone
can figure out how to do this, please let me know.)
</blockquote>
<blockquote>On some Windows systems, using UTF‑8 doesn't seem to work. In
this case, a Windows character set may be the best alternative: For instance,
for Windows Latin1 (cp1252) type "<code>chcp 1252</code>" in the console to
switch to cp1252, then run exiftool with "<code>-charset cp1252</code>" (or
<code>-L</code>). This same technique can be used for other supported Windows
code pages.</blockquote>
<a name="Q19"></a>
<p>19. <b>"How do I change the format of an extracted tag value?"</b></p>
<blockquote>The exiftool application has built-in options which allow you to
disable print conversions (<code>-n</code>), escape special HTML characters
(<code>-E</code>), and change the date/time (<code>-d</code>) and GPS coordinate
(<code>-c</code>) formats, but sometimes more control is needed over the
formatting of a value. In this case, user-defined Composite tags may be used to
define custom formatting on a per-tag basis. Here is a basic config file
example to illustrate the idea:
<pre>%Image::ExifTool::UserDefined = (
'Image::ExifTool::Composite' => {
MyArtist => {
Require => 'Artist',
ValueConv => '$val =~ tr/ /_/; $val',
},
},
);
1; # end
</pre>
The above config file defines a new tag called "MyArtist" which takes its value
from the "Artist" tag after translating spaces to underlines. So, for example, an
Artist value of "Phil Harvey" yields a corresponding MyArtist value of
"Phil_Harvey". The ValueConv expression may be any valid Perl expression -- it
returns the converted value given the original value ($val) of the Require'd tag.
</blockquote>
<blockquote>To activate the config file, it must be named
"<code>.ExifTool_config</code>" and placed either in your home directory or in
the same directory as the exiftool application. Note that the file name begins
with a "<code>.</code>", so if you are in Windows or on a Mac you may need to
rename the file from the command line since the GUI might not like file names
beginning with a "<code>.</code>".</blockquote>
<blockquote>User-defined Composite tags have many other features, including the
ability to combine the values of multiple tags. See the
<a href="config.html">config file documentation</a> for more details about
user-defined tags. Also, a
<a href="http://www.cpanforum.com/search/index.html?what=text&name=Image::ExifTool::UserDefined">quick
search of the CPAN forum</a> should reveal a number of user-defined tag examples.
</blockquote>
<a name="Q20"></a>
<p>20. <b>"ExifTool won't write an image due to errors"</b></p>
<blockquote>Minor errors may be ignored using the <code>-m</code> option, but
sometimes there are more serious errors which can't be ignored. ExifTool can be
used to fix these problems in JPEG images by deleting all metadata and
rebuilding it from scratch. The command looks like this:
<pre>exiftool -all= -tagsfromfile @ -all:all -unsafe bad.jpg
</pre>
where "<code>bad.jpg</code>" is the name of the image that requires fixing. This
command deletes all metadata then copies all writable tags that can be extracted
from the original image to the same locations in the new image. The
"<code>Unsafe</code>" tag is a <a href="TagNames/Shortcuts.html">shortcut</a>
for unsafe EXIF tags in JPEG images which are not normally copied.</blockquote>
<blockquote>After repairing an image like this you should be able to write to it
without errors, but note that some metadata from the original image may have
been lost in the process.</blockquote>
<hr>
<i>Last revised Jan. 6, 2010</i>
<p class='lf'><a href="index.html"><-- Back to ExifTool home page</a></p>
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