Imaging Resource interviewed the Sony engineer and manager Kimio Maki. The main talk was about the “The must-have sensor tech of the future” and the new 42MP sensor using on the new announced Sony a7RII. And in this interview, Kimio Maki told that sony is working on the uncompressed RAW and Sony could provide that via simple firmware upgrade! Good news!
Below are the key answers from Kimio Maki:
1) Why 42MP: 42-megapixel was the best pixel size to realize 4K movies. Super 35mm gives the best picture quality, from oversampling 15 megapixels down to the eight-megapixel 4K size. The picture quality is better than a professional video camera.
2) Noise improvement: in terms of ISO, this sensor’s sensitivity is better than 36-megapixel chips. The A7R Mark II has better noise performance; better than the A7R.
3) Why not 50MP: But 42 (MP) is not a good word. But actually, the engineers said “if you prefer 50, you have to lose sensitivity”. Of course 50 [would] give better resolution, and 45 would be more impressive, but it wouldn’t be perfectly balanced.
4) Advantages of backside illuminated sensors: in order to realize this kind of sensitivity, we have to prefer backside-illuminated. That’s the first priority, to gather lots of light, more light, effectively. The other decision was in the wiring layers; we used to use the aluminum, but aluminum is not good enough to transfer the data faster. Therefore we change the material from the aluminum to the copper to make it faster. [Ed. Note: Copper is more conductive than aluminum, so there’s less resistance in the circuit lines on the chip, meaning signals can propagate faster.] Therefore, then we could get a faster transition from the light to an electrical signal.
5) Uncompressed RAW: Sony RAW is compressed, not uncompressed. But if we’re getting a lot of requests for it, we should make such a kind of no-compression raw. We recognize the customer’s requirement, and actually we are working on it. And yes Sony could provide that via simple firmware upgrade!
6) Hybrid Autofocus: in terms of autofocus, we are using a hybrid focus, so first we use the phase-detection focus to get close to the object. Then near the object, we start to use contrast AF to get a clear peak. Then we adjust the focus. Then in order to make very precise focus (because 42-megapixel means very very small pixels), and also the focusing point could be a very small one, therefore we phase-detection together with contrast AF, contrast focus.
And the Imaging Resource editor writes the two demonstrations: A7R II autofocusing with a Canon lens and 4K video from the A7R II, in its Super35 crop mode. Read the full interview at Imaging Resource.