Ordinarily, Jewish women would be expected not to dance or sing with men looking on, or even present in the same area. However, at every Jewish wedding I have been to, there has been at least one male photographer/videographer on the women's side during the dancing, and the women go on presumably exactly as they would (singing, dancing) had there been no males there.
Is this allowed? (Does it depend at all on whether the photographer is Jewish?) Why or why not? If not, how could one reconcile the mitzvah of hachnosas kallah on that day with the needs of modesty?