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--- jpegtran.1.exif 1997-08-03 22:01:01.000000000 +0200
+++ jpegtran.1 2003-09-30 14:35:36.000000000 +0200
@@ -161,6 +161,14 @@
Copy all extra markers. This setting preserves miscellaneous markers
found in the source file, such as JFIF thumbnails and Photoshop settings.
In some files these extra markers can be sizable.
+See 'EXIF FILES' for special tratement of EXIF markers.
+.TP
+.B \-copy exif
+This setting preserves the EXIF marker, commonly found in JPEG files produced
+by digital cameras, in addition to any comment markers. If there is an EXIF
+marker it is copied and the JFIF marker (incompatible with EXIF) is
+omitted. If there is no EXIF marker a JFIF one is emitted as usual. See 'EXIF
+FILES' for special tratement of EXIF markers.
.PP
The default behavior is
.BR "\-copy comments" .
@@ -189,6 +197,26 @@
.B \-debug
Same as
.BR \-verbose .
+.SH EXIF FILES
+The EXIF variety of JPEG files, which are often produced by digital cameras,
+are recognized by jpegtran as EXIF files (i.e. not as JFIF, the
+usual variety of JPEG files). If the input file is recognized as EXIF (i.e.,
+there is an EXIF marker and no JFIF marker) the '-copy exif' option is
+automatically turned on if '-copy comments', or no '-copy' option, was
+specified. Thus, unless '-copy none' is specified an EXIF file is kept as EXIF
+and not converted to JFIF.
+.PP
+If a geometrical transformation is applied (e.g., rotate, transpose) the EXIF
+width and height fields are set to the width and height of the output
+image. Furthermore, the orientation field is reset to one, meaning tha the
+orientation of the output image is upright (i.e. normal).
+.PP
+Note that an explicitely given '-copy exif' option will output an EXIF file if
+the input is an EXIF file that was saved as JFIF, and that the EXIF marker is
+still present. This option is useful for recovering EXIF files that where
+converted to JFIF by a non EXIF-aware software. Note however, that the data in
+the EXIF marker is not validated, unless a geometrical transformation is
+applied.
.SH EXAMPLES
.LP
This example converts a baseline JPEG file to progressive form:
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