Actually if you look at the trends from Leica, Canon and Nikon they are all moving to more and more FF models. You did bring up popularity?
More models doesn't equate to popularity.
🙂 It's about units sold.
By its nature, a silicon chip (sensor) the size of a full frame (24x36) costs about 13 times as much to produce as an APS-C sensor, in that ballpark anyway. I did the actual math calculations in a post here about two years ago. This is due to simple area differences (the larger the chip the fewer are on each wafer) and also due to yield differences. As the technology advances yields improve.
Ergo, this is one of the primary reasons why a full frame camera costs a lot more than APS-C. It's not the only factor of course. And ergo, why there are many more APS-C cameras sold into the market.
There are many reasons why Nikon and Canon are pushing full frame, not the least of which, is as technology progresses, they get to offer new models to their existing installed base. And when they buy into full frame, many of them have to buy lenses that work on full frame. Very few people are upgrading from Nikon 5100s to 5200s, there simply isn't enough advancement between the models. In the old days, the D200 cost $2k; now you can get a D600 full frame for that. So as technology progresses, they have a ready market of people who will upgrade at the appropriate time that the customer chooses.
Since APS-C dominates the market, the technological advances are faster than they are with full frame. The same can be said when comparing full frame to medium format, but to a much greater degree. The number of medium format sensors sold into the marketplace is trivial, relatively speaking. The technological improvements are therefore much slower than in the high volume markets. This is why high ISO/low noise is far more advanced with the smaller sensors.
This is one reason why Apple moved to Intel processors a few years ago. It was extremely difficult to keep up with the technological advancement, because Intel was producing huge multiples of CPUs as compared to IBM and Mot PowerPC for Apple. The same concept applies, although in smaller ratios, between APS-C and full frame chips.
This huge volume advantage and resulting technological advancement is why many of the APS-C sensors sold today are extremly close to the performance of full frame sensors. Not equal, but for many applications, essentially little to no difference between the two.
This is the basis for my comment that APS-C is the 'new full frame.' The marketplace has spoken.
🙂
Just look at how often Leica introduces a new model...it's been 3 1/2 years between the M9 and the M. Or, how about the time frame between the D700 and the D800.
How many APS-C models have all the camera manufacturers introduced during those periods? It's an incredible pace.