EXIF Manipulation on the Linux commandline

I use jhead for manipulating EXIF data, renaming files and mogrify for
compressing the JPEG’s

the following command will rename all .jpg files in the current folder
to their corresponding “date taken” stamp in the format YYYYMMDD-HHMMSS

jhead -n%Y%m%d-%H%M%S *.jpg

Sometimes you have multiple cameras at a happy occasion, and wish to
collect all the images. But alas, one or more of the cameras have
their clock set to UTC, daylight savings time (winter when it is summer)
or similar. This will create annoyance as the images will not appear
fortunately you kan find the “sinner” and adjust the time with jhead
in a this way:

jhead *.jpg | grep "IXUS 700" -b4 | \
grep "File name" | sed "s/.*: //" | xargs jhead -ta+1

WARNING: This step is optional, just because I cannot tell the difference
between compressed and uncompressed images, maybe you can. A backup is
therefore recommended

The compression on digital cameras are not very efficient, and this
leads to large JPEG image files on your harddisk.
Fortunately you can use “mogrify” to cut JPEG’s down in size with

jhead -cmd "mogrify -quality 80 &i" *.jpg