The simpler media website CMS
I ran into a specific case of metadata preservation issue with cached images.
All images are jpg files
EXIF-IPTC-XMP metadata is present (copyrights, title, keywords etc)
IPTC copyright embedding - enabled
zpBase theme uses standard template-functions for:
printDefaultSizedImage - to display photo in full image page.
getFullImageURL() - to enable downloading original photo size in the same page, if option for Download was enabled.
If "Full image protection" is set to be used (Protected View or Download, "cache full image" enabled OR disabled) in Options->Image, getFullImageURL() leads to function getProtectedImageURL to be used and resulting image lacks ALL metadata, despite enabling IPTC preservation.
So, this generation of filename_FULL version lacks options to preserve metadata when it's essential for this use-case.