I have noticed that when reading Exif data from an image file (jpg), nothing is returned if a particular value is empty - i.e. Camera Model Name. I am using the returned data to create an array of values, so it is necessary that the array is always the same length and therefore has empty values returned as such. Is there an option flag that will do this, e.g. "exiftool -z"?
Use the -f option, this will print a dash if the tag doesn't exist. Check the documentation (http://www.exiftool.org/exiftool_pod.html) for more details. (I assume you already make use of e.g. the -T option?)
Thank you. At first, -f failed to work, and then I realised it was because I was specifying "exif:all" and not specifying the required tags individually. All is well now.