The inevitable demise of the DSLR as the mirrorless configuration becomes dominant in interchangeable lens cameras can be rightly considered yet another big change in the history of photography. While it’s unlikely anything will ever match the cataclysmic transition from film to digital, there have been plenty of shifts in the market that are just as dramatic as the switch from DSLR to mirrorless.
From the 1920s through to the early 1960s, the twin lens reflex configuration reigned supreme in rollfilm cameras. Just about every major camera maker - and quite a few smaller ones - built TLRs and the legendary Rolleiflex in particular was the choice of professionals in most fields of practice. As the name suggests, the TLR employs two lenses of the same focal length, arranged one above the other. The lower lens is the ‘taking’ lens, while the upper lens is the viewing lens, behind which is a fixed mirror set at 45º to reflect the image up to a focusing screen. The mirror, of course, accounts for the word “reflex” and the twin lens arrangement was designed to give a viewfinder image that was very close to the one that was recorded by the taking lens. There is some parallax error - the slight difference in the two lenses’ fields-of-view - but it was negligible when focusing over long distances. It
