This is a backside illuminated but, more importantly, it's a stacked sensor. This should result in performance on par with the Sony A1. I am hopeful we see it perform even better than the A1 - especially in low light. The main benefits to this stacked sensor design is extremely fast readout speeds - think minimal visual distortion with electronic shutter - and, on paper, backside illumination should reduce image noise. I stress "on paper" because that has been the idea from Sony for its sensors using this design, but it hasn't really demonstrated a monumental leap in the real world. I would argue that the stacked sensor readout speed is the most important aspect of all of this.