The proposition auf is used if the context is a wedding celebration/party, especially when talking about guests. Example: Ich war auf einer Hochzeit[sfeier] = I attendend a wedding [party]. The preposition bei may be appropriate to various different context. I don't think there is a common description independent of context.
The latter sentence would be understood to mean that the person uttering the sentence took pictures at the ceremony and at the wedding party.
The former sentence would be more appropriate in the context of describing the tasks of a wedding photographer, which includes taking pictures and shooting videos in various settings and not only at the ceremony and the wedding party.
ok. Thanks! I think that the usage of "an" and "zu" and "bei" with certain celebrations is a little confusing. It seems that two or even more are sometimes possible such as "zu Weihnachten" and "an Weihnachten" or "beim Geburtstag", "am Geburtstag" and "zum Geburtstag".
Or with this part (zu / an / bei) , should I start a new thread?