If you wish to use the `--caption` flag to add image captions read from EXIF comment metadata you will need a utility called `exiftool`.
You can install it via your package manager. For other options please consult the website: [https://www.sno.phy.queensu.ca/~phil/exiftool/](https://www.sno.phy.queensu.ca/~phil/exiftool/)