Photographers during the 19th and early 20th centuries usually imprinted or embossed onto their photographs their "photographer stamp." This stamp usually bore the photographer's name and location (city and state, or city and province if Canadian, or just the city). This information provides invaluable data to use to archive photographs and through which to search when it is compliled in a searcheable database.
It was common for photographers to have started out independently and then to have merged with another photographer. In such a case, their stamp may change from displaying their sole last name (e.g. "Anderson") to a combined name (e.g. "Anderson & Smith"). When photographers merge or seperate, Visual Ancestor considers those moves significant enough to warrant listing them as separate and distinct studios. In addition, a company name may appear on some of their stamps (e.g. "The Elite Photograph Studio"), but the appearence of a company name on some stamps does not necessarily warrant a separate and distinct studio, but rather it enhances the information about an existing photographer's location.
To complicate matters, photographers may have operated multiple locations in the same city throughout time, or in different cities altogether. This can be deduced by the photographer stamp when it displays multiple locations. Visual Ancestor names a photographer using a 5-digit number (for example, photographer 20028), and also records all known locations of the same photographer by a different enumerated location number (for example, locations 1 and 2).
Throughout a photographer's career, the photographer may move their studio just a few doors down on the same street (e.g. from 101 to 103 Main St.). When this happens, Visual Ancestor considers the move to be small enough to consider it the same studio at the same basic location, and combines the addresses together (e.g. 101 & 103 Main St.). However, when a photographer moves their studio to a different street in the same city, Visual Ancestor considers that large enough to warrant listing the photographer at two different locations (e.g. 1 and 2).