For years the mainstream of digital photographers clamored for a “full-frame” sensor. The smaller 15mm x 24mm sensors in digital SLRs since 1999 were too small, they claimed. When were we going to see a “real” sensor? Eventually the camera industry responded, and by 2007, both Canon and Nikon had cameras that sported 36mm x 24mm sensors. The reason this sensor size was regarded as “real” is that before digital, this was the size of the frame in 35mm film photography. This is also why, in my opinion, it is specious to regard this size as the gold standard of photography.
35mm photography represents an arbitrary compromise from the outset: it was originally intended to take advantage of left over 35mm motion picture film, in a way that let snapshot photographers use small, inconspicuous cameras that were easy to understand. 35mm was not, by its design, meant to be a bellwether of quality. It was intended to be convenient.
Photographers who claim to “need” the so-called full-frame sensors are missing the bigger picture: it’s a compromise. If they really want top quality, they should pine for some of the larger-format digital systems offered by companies like Phase One and Hasselblad, and quit trying to make digital photography like in the “old days” of film. If, on the other hand, they desire the convenience and affordability of smaller formats, the so-called “DX”-sized sensors, also known as APS-C, or even the new 4/3 sensors, make perfect sense.
In the end, it is ironic that lots of photographers will pay a huge premium for a lame compromise.