Card processing
The visible card fields are extracted for the workflow that asked for them, then the image stays in your SharePoint library.
Payment cards
Card fields, captured once.
When a process needs the details printed on a credit or debit card, iDoc reads those fields. Keep them only as long as that process requires.
Try it on your own files.
Bring samples to a 30-minute session. Crest will say whether this use case fits the documents you receive.