Also, there’s a script available (for DEVONthink, not DTTG!) which can copy metadata (not only EXIF, but also ICMP etc) to DT metadata or custom metadata fields.
Which image metadata are available
Digital images can contain a lot of metadata. Best known are probably the location (where the image was taken), the dimensions (width and height in pixels) and parameters like exposure time, focal length and aperture value. In addition, there can be keywords defined for an image, a copyright notice, a title, or the author. Although this sounds exciting, it is a lot less so if you try to retrieve these parameters by scripting.
Long story short: Only a few of a…