Not only because “meta data” has such a nice pronunciation, it is a very important part of every digital image captured. Well, obviously because you need to know when you have taken the shot but there is a lot more to learn.
More recently cams (read camera NOT smartphone!) do get integrated GPS receiver. This is nice, there are also other tools that I might post about some other time to sync e.g. a trip you recorded with your phone and with your photos, but today I want to talk about Exif data, which stands for Exchangeable image file format. Or the lack of it.
You may know that there are some basic fields, e.g. manufacturer, orientation, FNumber or Exposure time, that I at least like to check on flickr when looking at other photos. Sometimes I can learn from that.
But I recently noticed that The Gimp strips Exif information from tiff files. There is a workaround that says you can convert the image inside Gimp into e.g. jpeg and go from there – but lets assume you want to work with tiff (lossless) to e.g. further retouch the image in another program and the Exif data are gone.
So, here comes exiv2 to your rescue! It is available for Linux and Mac and lets you easily extract info from e.g. your RAW file and put it into your tiff/jpeg or other file.
So you might want to do something like this, assuming you are working with Canon RAW files (Nikon users imagine a .nef file):
me@mymachine :~$ exiv2 ex IMG_0000.CR2
me@mymachine :~$ exiv2 in IMG_0000.jpg
NOTE: The ex option will create a binary file named after the image (IMG_0000.exv). To actually work like this the exiv file and the target file should be named alike.
You can do a lot of other stuff, e.g. changing only single values (date) but you should check the man page for more details and experiment a little. Have fun.