Assuming the wedding photographer does only Catholic weddings (which is a big assumption as a wedding photographer is likely going to be serving couples of all different religions and no religion in order to make a living) , then if the Catholic pastor believes modesty to be a recurring issue with Catholic brides, then the pastor or the associate priest or deacon working with the couple to plan the wedding will provide guidelines about what clothing is acceptable for a church wedding. It is not up to the wedding photographer to police the clothes on the bride. If he did so as deacon it would be promulgating whatever guidelines come down from the pastor, and would not be a special concern of either a deacon or a wedding photographer.
Having a wedding-related profession raises a whole host of issues if the person is also going to take up Catholic ministry and as someone else said, this isn’t about modesty. For one thing, it is unlikely that a Catholic wedding photographer is going to be able to just limit his work to Catholics unless he lives in some town with a 99 percent Catholic population, and even then there’s likely to be a couple of atheists walk in the door sometime wanting some nice pictures down at the courthouse.