exiftool-vendored.pl

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd"> <html> <head> <title>ExifTool FAQ</title> <link rel=stylesheet type='text/css' href='style.css' title='Style'> <style type="text/css">  </style> </head> <body> <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">ExifTool doesn't read/write properly</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 and image quality</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> <li><a href="#Q21">Newlines in values</a></li> <li><a href="#Q22">Order of operations</a></li> <li><a href="#Q23">"0 image files updated"</a></li> <li><a href="#Q24">Date/time gets reset to today</a></li> <li><a href="#Q25">Image validation</a></li> <li><a href="#Q26">Import from database</a></li> <li><a href="#Q27">Windows .BAT file problems</a></li> <li><a href="#Q28">Copying a shifted date/time</a></li> </ol> </div> <h1 class='up'>ExifTool FAQ</h1> <a name="Q1"></a> 1. "Is there a forum for discussing ExifTool issues?" <blockquote> ExifTool issues can be discussed on the ExifTool forum at <a href="http://u88.n24.queensu.ca/exiftool/forum/">http://u88.n24.queensu.ca/exiftool/forum/</a> </blockquote> <a name="Q2"></a> 2. "How do I determine the tag name for some information?" <blockquote>When you run exiftool, by default it prints descriptions, not tag names, for the information it extracts. These descriptions are in English unless the <code>-lang</code> option is used to select another language. Note that descriptions often contain spaces between words, but tag names never do. Also, tag names are always English, regardless of the <code>-lang</code> setting. To print the tag names instead instead of descriptions, use the <code>-s</code> option when extracting information. eg) <pre>exiftool -s image.jpg</pre> Valid characters in tag names are <code>A-Z</code>, <code>a-z</code>, <code>0-9</code>, <code>_</code> and <code>-</code>. See the <a href="TagNames/index.html">tag name 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> 3a. "ExifTool reports the wrong value or doesn't extract a tag", 3b. "ExifTool doesn't write a tag properly", or 3c. "Other software can't read information written by ExifTool" <blockquote>[Also see <a href="#Q23">FAQ number 23</a> for reasons why ExifTool may not write some tags to certain file types.]</blockquote> <blockquote>First, make sure you are looking at the right information. Use ExifTool with a command like this to extract all information from the file, along with the location it was written: <pre>exiftool -a -G1 -s c:\images\test.jpg</pre> 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>-s</code> shows the tag names instead of their descriptions. (Substitute the path name of your file in place of "<code>c:\images\test.jpg</code>".)</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 (with the <code>-a</code> and <code>-G1</code> options) to determine where the information was written. Once you know where it should go, you can use ExifTool to write to this location. You can read or write information in a specific location by prefixing the tag name on the command line with the desired group name. eg.) "<code>-ExifIFD:DateTimeOriginal</code>" </blockquote> <blockquote>This problem may also occur if contradictory information exists in different meta information formats within the same file. For example, often XMP will be ignored if IPTC exists and the Photoshop:IPTCDigest does not agree with the IPTC content. The <a href="http://www.metadataworkinggroup.org/">Metadata Working Group</a> recommends techniques to keep the EXIF, IPTC and XMP metadata synchronized. These recommendations are implemented by the ExifTool <a href="TagNames/MWG.html">MWG tags</a>. For maximum compatibility with the widest range of applications, it is suggested that these MWG tags be used whenever possible.</blockquote> <blockquote>One final note: When writing, the <code>-v2</code> option may be useful because it provides details about what ExifTool is writing, and where. </blockquote> <a name="Q4"></a> 4. "ExifTool reports more than one shutter speed or aperture value, and they are slightly different" <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> 5. "How do I format date and time information for writing?" <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> Having said this, ExifTool is very flexible about the actual format of input date/time values when writing, and will attempt to reformat any values into the standard format unless the <code>-n</code> option is used. Any separators may be used (or in fact, none at all). The first 4 consecutive digits found in the value are interpreted as the year, then next 2 digits are the month, and so on. [The year must be 4 digits. Other fields are expected to be 2 digits, but a single digit is allowed if the subsequent character is a non-digit.] For EXIF date/time values, all 6 date/time fields must exist ("<code>YYYYmmddHHMMSS</code>"), but XMP date/time values require only the year ("<code>YYYY</code>"). This feature facilitates useful operations such as setting date/time tags from a date embedded in the file name. For example, the command <pre>exiftool "-alldates<filename" c:\images</pre> will set the common date/time tags from the file name for all images in the directory "<code>c:\images</code>". This will work for any file name which matches the above criteria (eg. "IMG_20110927_103000.jpg"). [AllDates is a shortcut for 3 tag names: DateTimeOriginal, CreateDate and ModifyDate. See the <a href="TagNames/Shortcuts.html">Shortcuts Tags documentation</a> for more information.]</blockquote> <blockquote>The <code>-d</code> option provides additional flexibility in parsing strings when writing date/time tags if POSIX::strptime or Time::Piece is installed and the ExifTool version is 10.32 or later (use "<code>exiftool -ver -v</code>" to check the installed packages). The format of the <code>-d</code> argument is the same for reading and writing.</blockquote> <blockquote>Special feature: A value of "<code>now</code>" may be used to represent the current time when writing any date/time tag. For example: <pre>exiftool -xmp:dateTimeOriginal=now a.jpg</pre> [There is also a <a href="TagNames/Extra.html">Now tag</a> which may be used for a similar purpose by copying its value to another tag, but copying tags adds an extra read stage to the processing which is best avoided if performance is an issue.] </blockquote> <a name="Q6"></a> 6. "I get '<code>Can't convert TAG (not in PrintConv)</code>' errors when writing a tag" <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 Values 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 [with the possible exception of list-type tags -- see <a href="#Q17">FAQ number 17</a> below], so a value that is printed as 'Above Sea Level' must also be written in that form. (In other words, 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, eg) <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 equivalent: <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></blockquote><blockquote class=prog> Programmers: These techniques look like this when calling Image::ExifTool functions from a Perl script: <pre>$exifTool->SetNewValue(flash => 1, Type => 'ValueConv'); $exifTool->SetNewValue(flash => 0x1, Type => 'ValueConv'); $exifTool->SetNewValue('flash#' => 1); $exifTool->SetNewValue('flash#' => 0x1); $exifTool->SetNewValue(flash => 'fired'); </pre></blockquote> <a name="Q7"></a> 7. "I can't delete all EXIF information from a TIFF file using '<code>exiftool -exif:all= img.tif</code>'" <blockquote>This is because of the way a TIFF file is structured. With a JPEG image, this command removes 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. The same is true for any TIFF-based RAW file such as DNG, CR2, NEF, etc. For these types of files, ExifTool just deletes the ExifIFD subdirectory, so any information stored in other directories is preserved (BUT NOTE THAT WITH PROPRIETARY RAW FORMATS THIS MAY DELETE INFORMATION THAT IS NECESSARY FOR PROPER RENDERING OF THE IMAGE). </blockquote> <blockquote>Use "<code>exiftool -a -G1 -s img.tif</code>" to see where the information is stored. Any tags remaining in other IFD's must be deleted individually from a TIFF-format file if desired. For convenience, a <a href="TagNames/Shortcuts.html">shortcut tag</a> is provided to simplify the deletion of common metadata tags from IFD0 by adding "<code>-CommonIFD0=</code>" to the command line. </blockquote> <a name="Q8"></a> 8a. "All maker note information is lost if I change the Make or Model tag", or 8b. "I can't copy maker note information to an image", or 8c. "I can't view a RAW image after changing the model tag" <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 (which, for a RAW image, may mean that the image can no longer be properly rendered). 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. eg) <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. Since maker note tags may not be created individually, they must instead be copied as a block with "<code>-makernotes</code>".) </blockquote> <a name="Q9"></a> 9a. "The information is different when I copy all tags to a new file", or 9b. "The tag locations change when I use <code>-tagsfromfile</code> to copy information" <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 general 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 family 1 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> In this command, since no destination tag was specified, the destination is the same as the source (ie. "<code>-all:all>all:all</code>"), so the information is copied to the same family 1 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># copy all tags to preferred groups (no destination group) 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 # copy all tags, preserving family 1 group (destination group 'all') 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 # copy all tags to EXIF group (destination group 'exif') # [the destination family 1 group is the preferred EXIF IFD] exiftool -tagsfromfile src.jpg "-all>exif:all" dst.jpg exiftool -tagsfromfile src.jpg "-all:all>exif:all" dst.jpg # copy XMP tags to XMP group (destination group 'xmp') # [the destination family 1 group is the preferred XMP namespace] exiftool -tagsfromfile src.jpg "-xmp:all" dst.jpg exiftool -tagsfromfile src.jpg "-xmp:all>xmp:all" dst.jpg # copy XMP tags, preserving family 1 group (destination group 'all') exiftool -tagsfromfile src.jpg "-xmp:all>all:all" dst.jpg # copy XMP tags to preferred groups (no destination group) exiftool -tagsfromfile src.jpg "-xmp:all>all" dst.jpg # copy XMP tags to EXIF only (destination group 'exif') # [the destination family 1 group is the preferred EXIF IFD] 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> <blockquote>Certain types of meta information (such as EXIF, IPTC, XMP and ICC_Profile) may also be copied as a block. This technique copies all meta information, even if ExifTool doesn't have the ability to write some individual tags contained in the block. For all block types except EXIF, the metadata is copied byte-for-byte from the original image. With EXIF however, the metadata may be restructured to ensure that it is self-contained. Also note that EXIF may not be written as a block to TIFF-based file formats. Beware that any existing metadata of this type in the distination file will be overwritten by the new block. <pre># copy EXIF as a block between same-named JPG files in different directories exiftool -tagsfromfile SRCDIR/%f.%e -exif -ext jpg DSTDIR # copy XMP as a block from one file to another exiftool -tagsfromfile src.jpg -xmp dst.cr2 </pre></blockquote> <a name="Q10"></a> 10. "How does ExifTool handle coded character sets?"   <blockquote>[Also see <a href="#Q18">FAQ number 18</a> for help on displaying special characters in a Windows console.]</blockquote> <blockquote>Certain meta information formats allow coded character sets other than plain ASCII. When reading, most known encodings are converted to the external character set according to the exiftool "<code>-charset CHARSET</code>" or <code>-L</code> option, or to UTF‑8 by default. When writing, the inverse conversion is performed. Alternatively, special characters may be converted to/from HTML character entities with the <code>-E</code> option. </blockquote> <blockquote>A distinction is made between the external character set visible to the ExifTool user, and the internal character used to store text in the metadata of a file. These character sets may be specified separately as follows: <ol><li>The external character set for tag values passed to/from ExifTool is UTF‑8 by default, but it may be changed through any of these command-line options: <blockquote><code>-charset CHARSET</code>   or   <code>-charset exiftool=CHARSET</code>   or   <code>-L</code> </blockquote> The encoding of file and directory names (eg. the FILE argument on the command line) is different. By default, these names are passed straight through to the standard C I/O routines without recoding. On Mac/Linux these routines expect UTF‑8, but on Windows they use the system code page (which is dependent on your system settings). However, as of ExifTool 9.79, the external filename encoding may be specified: <blockquote><code>-charset filename=CHARSET</code></blockquote> When this is done, file and directory names are converted from the specified encoding to one appropriate for system I/O routines. In Windows, this also has the effect of enabling Unicode filename support via the special Windows wide-character I/O routines if the required Perl modules are available (these are included in the Windows executable version of ExifTool). See <a href="exiftool_pod.html#WINDOWS-UNICODE-FILE-NAMES">WINDOWS UNICODE FILE NAMES</a> in the application documentation for more details. </li> <li>The internal character set for strings stored in file metadata may be specified for some metadata types: <blockquote><code>-charset TYPE=CHARSET</code></blockquote> (where <code>TYPE</code> is "<code>exif</code>", "<code>iptc</code>", "<code>id3</code>", "<code>photoshop</code>" or "<code>quicktime</code>")</li></ol> Valid <code>CHARSET</code> values are (with aliases given in brackets, case is not significant): <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> The <code>-L</code> option is equivalent to "<code>-charset Latin</code>", "<code>-charset Latin1</code>" and "<code>-charset cp1252</code>".</blockquote> <blockquote>Type-specific details are given below about the special character handling for EXIF, IPTC, XMP, PNG, ID3, PDF, Photoshop, QuickTime, AIFF, RIFF, MIE and Vorbis information:</blockquote>  <blockquote>EXIF: Most textual information in EXIF is stored in ASCII format (called "string" in the <a href="TagNames/index.html">ExifTool tag name documentation</a>). By default ExifTool does not convert these strings. However, it is not uncommon for applications to write UTF‑8 or other encodings where ASCII is expected. To deal with these, ExifTool allows the internal EXIF string encoding to be specified with "<code>-charset exif=CHARSET</code>", which causes EXIF string values to be converted from the specified character set when reading, and stored with this character set when writing. The <a href="http://www.metadataworkinggroup.org/">MWG</a> recommends using UTF‑8 encoding for EXIF strings, and in keeping with this the "<code>-use mwg</code>" feature sets the default internal EXIF string encoding to UTF‑8 (ie. "<code>-charset exif=utf8</code>"), but note that this will have no effect unless the external encoding is also set to something other than the default of UTF‑8.</blockquote> <blockquote>A few EXIF tags (UserComment, GPSProcessingMethod and GPSAreaInformation) support a designated internal text encoding, with values stored as ASCII, Unicode (UCS‑2) or JIS. When reading these tags, ExifTool converts Unicode and JIS to the external character set specified by the <code>-charset</code> or <code>-L</code> option, or to UTF‑8 by default. ASCII text is not converted. When writing, text is stored as ASCII unless the string contains special characters, in which case it is converted from the external character set (UTF‑8 by default), and stored as Unicode. ExifTool writes Unicode in native EXIF byte ordering by default, but the byte order may be specified by setting the ExifUnicodeByteOrder tag (see the <a href="TagNames/Extra.html">Extra Tags documentation</a>).</blockquote> <blockquote>The EXIF "XP" tags (XPTitle, XPComment, etc) are always stored internally as little-endian Unicode (UCS‑2), and are read and written using the specified external character set.</blockquote>  <blockquote>IPTC&dagger;: 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 the internal IPTC encoding is assumed to be Windows Latin1 (cp1252), but this can be changed with "<code>-charset iptc=CHARSET</code>". When reading, these strings are converted to UTF‑8 by default, or to the external character set specified by the <code>-charset</code> or <code>-L</code> option. When writing, the inverse conversions are performed. No conversion 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 converted if an ISO 2022 shift code is encountered. See the <a href="http://www.iptc.org/std/IIM/4.1/specification/IIMV4.1.pdf">IPTC IIM 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 (from Windows Latin1 unless CodedCharacterSet was already "UTF8"): <pre>exiftool -tagsfromfile @ -iptc:all -codedcharacterset=utf8 a.jpg </pre>or from Windows Latin2 (cp1250) to UTF‑8: <pre>exiftool -tagsfromfile @ -iptc:all -codedcharacterset=utf8 -charset iptc=latin2 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 to Windows Latin2: <pre>exiftool -tagsfromfile @ -iptc:all -codedcharacterset= -charset iptc=latin2 a.jpg </pre>Note that unless CodedCharacterSet is UTF‑8, applications have no reliable way to determine the IPTC character encoding. For this reason, it is recommended that CodedCharacterSet be set to "<code>UTF8</code>" when creating new IPTC.</blockquote> <blockquote class='sm'>&dagger; Refers to the older <a href="http://www.iptc.org/site/News_Exchange_Formats/IIM/">IPTC IIM</a> format. The more recent <a href="http://iptc.cms.apa.at/site/Photo_Metadata/IPTC_Core_&_Extension/">IPTC Core and Extension specifications</a> actually use the XMP format (see below). </blockquote>  <blockquote>XMP: 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 conversion is performed, however the <code>-charset</code> or <code>-L</code> option may be used used to convert text to/from a specified external character set when reading/writing.</blockquote> <blockquote>PNG: <a href="TagNames/PNG.html#TextualData">PNG TextualData tags</a> are stored as tEXt, zTXt and iTXt chunks in PNG images. The tEXt and zTXt chunks use ISO 8859-1 encoding, while iTXt uses UTF‑8. When reading, ExifTool converts all PNG textual data to the external character set specified by the <code>-charset</code> or <code>-L</code> option, or to UTF‑8 by default. When writing, ExifTool generates a tEXt chunk (or zTXt with the <code>-z</code> option) if the text doesn't contain special characters or if Latin encoding is specified (<code>-L</code> or <code>-charset latin</code>); otherwise an iTXt chunk is used and the text is converted from the specified external character set and stored as UTF‑8.</blockquote> <blockquote>JPEG Comment: The encoding for the JPEG Comment (COM segment) is not specified, so ExifTool reads/writes this text without conversion.</blockquote> <blockquote>ID3: 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 converts ID3v1 text from Latin to the external 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 converts ID3v2 text from this encoding to the external 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>PDF: PDF text strings are stored in either PDFDocEncoding (similar to Windows Latin1) or Unicode (UCS‑2). When reading, ExifTool converts to the external 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>Photoshop: Some Photoshop resource names are stored as Pascal strings with unknown encoding. By default, ExifTool assumes MacRoman encoding and converts this to UTF‑8, but the internal and external character sets may be specified with "<code>-charset Photoshop=CHARSET</code>" and "<code>-charset CHARSET</code>" respectively.</blockquote> <blockquote>QuickTime: QuickTime text strings may be stored in a variety of poorly documented formats, and ExifTool does its best to decode these according to the <code>-charset</code> option setting. For some QuickTime strings where the internal encoding is not known, ExifTool assumes a default encoding of MacRoman, but this may be changed with "<code>-charset QuickTime=CHARSET</code>".</blockquote> <blockquote>AIFF: AIFF strings are assumed to be stored in MacRoman, and are converted according to the <code>-charset</code> option when reading. </blockquote> <blockquote>RIFF: The internal encoding of RIFF strings (eg. in AVI and WAV files) is assumed to be Latin unless otherwise specified by the RIFF CSET chunk or the "<code>-charset RIFF=CHARSET</code>" option. </blockquote> <blockquote>MIE: MIE strings are stored as either UTF‑8 or ISO 8859‑1. When reading, UTF‑8 strings are converted according to the <code>-charset</code> or <code>-L</code> option, and ISO 8859‑1 strings are never converted. When writing, input strings are converted 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> <blockquote>Vorbis: Vorbis comments are stored as UTF‑8, and are converted to the character set specified by <code>-charset</code> or <code>-L</code> when reading.</blockquote> <blockquote class=prog> Programmers: ExifTool returns all values as byte strings of encoded characters. Perl wide characters are not used. The encoding is UTF‑8 by default, but valid UTF‑8 can not be guaranteed for all values, so the caller must validate the encoding if necessary. The encodings described above are set by the various <a href="ExifTool.html#Charset">Charset options</a> of the API. Note: Some settings of the system PERL_UNICODE environment variable may be incompatible with ExifTool's character handling. </blockquote>   <a name="Q11"></a> 11. "My user-defined tags don't work" <blockquote> For examples of how to add user-defined tags, see the <a href="config.html">ExifTool_config</a> file in the ExifTool distribution. It may be useful to activate this file as a test before trying to implement your own config file. To activate this file, copy it to your HOME directory then rename it to "<code>.ExifTool_config</code>". <blockquote class=lt>Note: The config file must be renamed at the command line because neither the Windows nor Mac GUI allow a file name to begin with a "<code>.</code>". To do this in Windows, run "cmd.exe" and type the following (pressing RETURN at the end of each line): <pre>cd %HOMEPATH% rename ExifTool_config .ExifTool_config </pre> or on a Mac, open the "Terminal" application (from the /Applications/Utilities folder) and type this command then press RETURN: <pre>mv ExifTool_config .ExifTool_config </pre></blockquote> With the sample config file installed, you should be able to write the example tags. A command like this: <pre>exiftool -v2 -NewXMPxmpTag=test FILE</pre> should print this as the first line of its output: <pre>Writing XMP-xmp:NewXMPxmpTag </pre> If this doesn't work, the most common problem is that the "<code>.ExifTool_config</code>" configuration file isn't getting loaded. In this case, there are a few things you can try: <ol> <li>Make sure the config file name is correct. It must be "<code>.ExifTool_config</code>" (note the leading "<code>.</code>", and the capital "<code>T</code>").</li> <li>Set either the HOME or the EXIFTOOL_HOME 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! See the note above for help renaming the config file.)</li> <li>If you can't get the config file to load automatically, you can try loading it manually with the exiftool <code>-config CFGFILE</code> option. (Note: This must be the first option on the command line.) This allows loading of a config file with any name.</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 this type of information.</blockquote> <blockquote>Note that all tag names in the config file are case sensitive. Specifically, the case must be correct for tag names in Composite tag Require/Desire entries. Also note that XMP tag names are generated automatically by capitalizing the tag ID unless the tag definition contains a "Name" entry.</blockquote> <blockquote class=prog>Programmers: To specify the config file directory from within a Perl script when using the ExifTool API, set the EXIFTOOL_HOME environment variable before loading the ExifTool module: <pre>BEGIN { $ENV{EXIFTOOL_HOME} = '/config_file_directory' } use Image::ExifTool; </pre> Also see the <a href="ExifTool.html#Config">Configuration section of the ExifTool API documentation</a> for techniques to use a config file with another name, or to disable the config file feature. </blockquote> <a name="Q12"></a> 12. "How do I export information from exiftool to a database?" <blockquote>[See <a href="#Q26">FAQ number 26</a> for help with the reverse -- importing metadata from a database.]</blockquote> <blockquote> It is often easiest to export information formatted as a tab-delimited or comma-separated list of values using the exiftool <code>-T</code> or <code>-csv</code> option. As well, the <code>-r</code> option is useful for recursing through all images in a hierarchy of directories. For example: <pre>exiftool -T -r -filename -exposuremode -ISO t/images > out.txt </pre> This command recursively processes all images in the "<code>t/images</code>" directory, extracting FileName, ExposureMode and ISO tags, and writing the output to a tab-delimited text file called "<code>out.txt</code>". After the command has executed, "<code>out.txt</code>" will look something like this: <pre>Canon.jpg Manual 100 Casio.jpg - 64 Nikon.jpg - 100 OlympusE1.jpg Auto 400 </pre> One limitation of the <code>-T</code> option is that a list of tags to extract must be specified. Otherwise, all information is extracted from each input file, and the columns would contain values from random tags.</blockquote> <blockquote> The <code>-csv</code> (comma separated values) option solves this dilemma by pre-extracting information from all input files, then producing a sorted list of available tag names as the first row of the output, and organizing the information into columns for each tag. As well, a first column labelled "SourceFile" is generated. These features make it practical to use the <code>-csv</code> option for extracting all information from multiple images. For example, this command: <pre>exiftool -csv -r t/images > out.csv</pre> gives an output like this: <pre>SourceFile,AEBBracketValue,AELock,AFAreaHeight,AFAreaMode,AFAreas,[...] t/images/Canon.jpg,0,,151,,,[...] t/images/Casio.jpg,,,,,,[...] t/images/Nikon.jpg,,,,Single Area,,[...] t/images/OlympusE1.jpg,,Off,,,"Center (121,121)-(133,133)",[...] </pre> Note that the number of columns in the <code>-csv</code> output may be very large if all information is extracted. Missing tags are indicated by empty strings as in the example above, or by dashes if the <code>-f</code> option is used.</blockquote> <blockquote> It should be possible to import these files 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>In Windows, a .BAT file containing the exiftool command may be used to give drag and drop functionality. Dropping a folder on the following .BAT file will create "out.txt" in the folder: <pre>echo "FileName<tab>Aperture<tab>ISO" > %1\out.txt exiftool -T -r -filename -aperture -ISO %1 >> %1\out.txt </pre> The "<code>echo</code>" command was included to add column headings to the output. (The tab character in the echo command, indicated by "<code><tab></code>", may be generated in Mac/Linux shells with CTRL-v then TAB, or in a Windows cmd shell with TAB when cmd.exe is run with the <code>/f:off</code> option to disable tab completion.) </blockquote> <blockquote>Other possible export formats include RDF/XML (with the the <code>-X</code> option), or JSON (with the <code>-j</code> option). These methods allow transfer of more complex data sets (including structured information with the <code>-struct</code> option), but require that the importing software supports these formats.</blockquote> <blockquote>Finally, the <code>-p</code> option may be used to generate any arbitrary output format. For example, the following format file (let's call it "<code>my.fmt</code>") may be used to emulate a CSV-formatted output: <pre>#[HEAD]FileName, Aperture, ISO $filename, $aperture, $iso </pre> with a command like this: <pre>exiftool -f -r -p my.fmt t/images > out.csv </pre> Alternatively, the <code>-p</code> option may be used with a format string instead of a file name. The following command has the same effect as above except that the row of headings is not printed (Note: Use single quotes as below on Mac/Linux, or double quotes instead on Windows): <pre>exiftool -f -r -p '$filename, $aperture, $iso' t/images > out.csv </pre> With the <code>-f</code> option, the value of any missing tag is printed as a dash. Without this option, missing tags generate a minor warning and the line in the <code>-p</code> output is not printed. The <code>-m</code> option may be used to ignore minor warnings, which causes these lines to be printed with an empty value for missing tags.</blockquote> <blockquote> See the <code>-p</code> option in the <a href="exiftool_pod.html">application documentation</a> for more information about this feature. </blockquote> <a name="Q13"></a> 13a. "Why is my file smaller after I use ExifTool to write information?", or 13b. "Why do some Offset tags change value when I write other tags?", or 13c. "How does editing a file with ExifTool affect image quality?" <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, or so that some tags are stored at different offsets in the file.</blockquote> <blockquote>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. [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 <code>out.html</code> in your web browser. Unused data blocks are brown in this output.] </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, but this padding is omitted if the <code>-z</code> option is used), 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 with ExifTool is "lossless" as far as the image is concerned.</blockquote> <a name="Q14"></a> 14a. "What format do I use for writing GPS coordinates?", or 14b. "How do I change the format of extracted GPS coordinates?" <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> <blockquote>When reading, ExifTool reports coordinates in the format <pre>DDD deg MM' SS.SS"</pre> where <code>DDD</code> is degress, <code>MM</code> is minutes, and <code>SS.SS</code> is seconds. The <code>-n</code> option may be used to change this to decimal degrees, or any arbitrary format may be specified with the <code>-c</code> option. See the <a href="exiftool_pod.html">application documentation</a> for details. </blockquote> <a name="Q15"></a> 15. "I get MakerNote warnings or errors when reading or writing information" <blockquote>Problems like this may be caused by image editing software which doesn't properly update offsets in the MakerNotes when rewriting an image. These offsets are used as pointers to reference tag values and structures within the metadata, and errors like this may lead to missing or incorrect values for some MakerNotes tags. In many cases, ExifTool will detect this type of problem and issue a warning like this when reading (or an error when writing): <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 to see them all, since by default only one warning is displayed per file.] </blockquote> <blockquote>This is a particularly insidious problem that is sometimes difficult for ExifTool to correct automagically, so it requires some operator intervention. If this warning occurs, you have a few alternatives:</blockquote> <blockquote>1) Use the <code>-F</code> option to allow ExifTool to attempt to fix the incorrect offsets. If ExifTool was correct in its diagnosis, then this option will fix the incorrect offsets. This is usually the appropriate choice if this problem was caused by editing the image with other software.</blockquote> <blockquote>2) Use the <code>-m</code> option to ignore the warning (or downgrade the error to a warning when writing). This causes ExifTool to honour the existing maker note offsets, and may be the correct choice if images straight out of the camera have this problem.</block