No, it is not a scanning service for your photos. Actually, I think the name Photoduplication is a poor way of referring to what is just a copy of a document on film. But, that is what they call it.
What they do is provide a digital copy of items in their catalog. If you go on the familysearch.org website, go into the catalog and you will see a list of their holdings on film. If you give them the film # and the name of the person you are researching and whether it is a birth,marriage or death certificate, they will send you a copy of a certificate via email. You will need to have the certificate number first before you can look up the film # in the catalog. It is a little bit of a process to look them up and takes some time, but after you do it a couple of times, it's easy. You can either mail, fax or email in your requests. No need to visit your local familiy history center.
I do much research in the NYC area and I am fortunate in that I use
www.italiangen.org or germangenealogygroup.com which provides a huge database of marriage, birth & death certificate #'s of various years for the 5 boroughs of NYC. Even at $2 a copy it was well worth going through familysearch than the New York City Municipal Archives, which I believe charges $15 for each certificate. Now there is no cost because they send the copies of certificates as a file in your email.
Here is the link from familysearch that explains the service:
https://www.familysearch.org/learn/wiki/en/index.php?title=P...Ellen