I would veture to guess, that is on the bride and the bride needs to pay for thephotographers time. If the photographer and the bride haveset a time, it needs to be planned for and honored. I think they charge a flat fee when they are hired to do everything, otherwise, it is by the hour.
It can work both ways Gloria!
Hourly fee: A wedding is a business that is accepted on an agreement - verbal or written. Therefore, whatever the agreement is for TIME on the job, it must be honoured. Now if you agree to a 5-hour wedding, then keep to it. Over that, then you'll have to pay the photographer for his or her time.
As it relates to flat fees, allowances are made for lateness, etc. and the price will reflect this.
My suggestion is that before you signed off on a photographer for your weeding, know what you are paying for. And this is done with the signing of a contract that lays out what is required of each parties... this will clear up all misunderstanding, concerns, etc.
Trust I was clear in my explanation, and that you now have a clearer understanding of how a photographer goes about is fees.