Toronto. In the late 1960s and early 1970s when camera collecting took off, a subset of collectors included photos in their collection. I think it was a bit random at the beginning, then collectors realized cased images like daguerreotypes and ambrotypes were one off. And more complicated to create. As a result collectors considered such old prints far more valuable.
With glass plate and later film negatives, many prints could be made from one negative giving credence to the saying, ‘cheaper by the dozen’. In time collectors realized that good clear prints were worth more than faded prints. Prints of famous people or by famous studios (eg Notman, Southworth & Hawes, etc) were more valuable. Size and rarity also added value.
The vast majority of prints were studio portraits so work scenes and outdoor scenes became more valuable than a run of the mill portrait. Some collectors chose only certain processes like the beautiful (even today) carbo process with its rich blacks, or well taken and printed stereo cards.
The folks in the photo at upper left are from a lot in the recent Port Colborne auction. A few decades ago, we used to joke that people buying such portraits could gain some ‘instant ancestors’. Today we know better and value these photos as a snap shot into history.