Please check this screen shot at http://bit.ly/1qjguF4 which is Wordpress’s default Media Library that provides entry fields for images to entry Meta data.
At right side there is “Caption” field. What is to be entered there ?
I have used this hero image at this link http://bit.ly/21TNak6
and you can get a fair idea of how this hero image is being used and what info entry will help to generate the suitable meta data.
Your feedback would be valued.