Twin-lens reflex (TLR) cameras were first introduced in the 1880s, but they did not become popular until the mid-20th century with the introduction of 120 medium format film. TLR cameras use two lenses, one for viewing and one for taking the photograph, with the image from the viewing lens being reflected onto a ground glass screen.
In the 1930s and 1940s, TLR cameras became more popular with the introduction of models from companies such as Rollei and Yashica. These cameras offered high-quality optics and were often used by professional photographers for portraiture and studio work.
In the 1950s and 1960s, TLR cameras became more affordable and widely available, with many amateur photographers using them for landscapes, street photography, and other types of photography. Some TLR cameras also offered features such as built-in light meters and automatic exposure modes.
However, with the rise of SLR cameras in the 1970s and the increasing popularity of smaller 35mm cameras, TLR cameras declined in popularity. Today, TLR cameras are considered a niche product, but they still have a loyal following among photographers who appreciate the unique shooting experience and high-quality optics that these cameras can offer.