It seems just silly to require the user to display a dialog to perform the editing, when the data is right there in front of her.
Perhaps a toggle option exposed at the top level of browser interaction would enable such editing, with "off" being the default for new users.
The behaviors I would expect include:
- 1. Automatic protection of camera contributed EXIF fields (shutter speeds, apertures, etc)
2. Ability to edit fields for a group of selected images simultaneously
3. An undo feature for edits that have not been written to the images
4. Access to metadata templates etc. from the browser info panels
5. Ability to switch to the modal dialog at any time, even in the midst of the edits
