It's a 15.36 MP x 3 Layers (~46MPs) Foveon Sensor in APS-C size, finally (but not 1.7X!). But since Foveon and the Sigma combination and combos had been proved to be a marketing failure in the past. I just wonder, if it really works for Sigma (and Foveon, which was acquired anyway) this time?!
Btw, I admire much the insistence and courage of Sigma the company. But however, I am not optimistic about the sales of this new camera, even it is meant to be a "flagship" (which still falls short of many things for being more updating)!