What are the relative merits of large studios vs. independents?
Quality of work and service are more important than size. Large studios offer resources and backup in case your assigned photographer gets sick. Some feel more comfortable in dealing with a larger, more substantial firm. Most employ subcontractors, many of whom use photography as a supplemental income source or are just learning the trade. Some big studios are geared to low-budget events. Small studios and independents excel at individualized personal service. You will most likely have your first contact directly with the actual photographer who will do your event. The advantage here is that your album will more closely reflect your personal wishes.
