Currently, information is written only in the outer-level document.
Photoshop will discard meta information in a PostScript document if it has
to rasterize the image, and it will rasterize anything that doesnt contain
the Photoshop-specific ImageData tag. So dont expect Photoshop to read
any meta information added to EPS images that it didnt create.
The following two acronyms may be confusing since they are so similar and
have different meanings with respect to PostScript documents:
DSC = Document Structuring Conventions
DCS = Desktop Color Separation