When photography became widespread and cameras began to be mass-manufactured, various instructional guides appeared on the market, and since then their number has grown steadily. In addition to the instruction manuals included with cameras, there were professional periodicals and how-to book. The information and advice they contained can be divided into two categories. They concerned either technological matters (the level of expertise depending on how technologically advanced the device in question was), or formal issues related to image composition. This information, and especially the illustrated materials that accompanied them, formed the canon of the prevailing photographic subjects. In the first half of the 20th century, the guidebooks became Bible-like authorities for amateurs, who knew how to take a 'good picture' thanks to them. Over time, when other equally valid aesthetics emerged, the term 'good picture' became more and more ambiguous. This was especially noticeable when the Internet became the primary means of distributing knowledge.