...contingency in our contract? The wedding photographer has put in the following contingency in the contract "No other photographer/photography shall be permitted while photographer is photographing any aspect of Wedding, Reception, or related activity (Individual guests with personal cameras excepted). " Is this standard operating procedure? What does this guy have to lose if he is being paid?
OK, so I should have probably added that this is being done as a barter situation; services were rendered in exchange for the wedding photo package. It is an all inclusive package that has already been "pre-paid". He stands to lose nothing.

It's standard. Basically, it means that you won't hire someone else to take pictures. It's ok for guests but not another professional.

He has to set up shots, lighting and guests.
Another photographer will interfere.
Its a very common clause.