Nikon and Canon have been synonymous with high-quality cameras for decades. But about five years ago, Sony’s imaging arm started a rapid ascent among serious hobbyists and even some pro photographers. Sony succeeded by committing heresy: It basically scaled up point-and-shoot cameras, giving them bigger image sensors and interchangeable lenses, but dispensing with the mirror that single-lens reflex cameras–digital models and, before them, film ones–use to bounce a preview image into an optical viewfinder. That’s allowed smaller, lighter Sony models to compete on image quality with their bulkier, more conventional DSLR competitors.

Now Sony is beating Nikon and even longtime top dog Canon in sales of interchangeable-lens cameras in the U.S.–not yet on the total number of units, but on the average price per camera sold. In July, the average price for a Sony mirrorless camera was $1,040, versus $831 for a Nikon DSLR and $793 for a Canon DSLR, according to data from the NPD Group. In July, Sony even beat both Canon and Nikon in total revenue for interchangeable-lens cameras in the U.S.

In other words, people are paying a premium for Sony’s technology. And with smartphones having killed off cheaper camera categories, the premium market is almost all that’s left.

The Z6 and Z7 pack full-frame image sensors. [Photo: courtesy of Nikon]

Today, Nikon is fighting back. It’s introducing its own pro-grade mirrorless models: the 24.5-megapixel Z6 (available in late November) and the 45.7-megapixel Z7 (out on September 27), selling for $1,996 and $3,400 (without lenses). Along with the cameras, it’s…