Canon Rumors said:
Hmm...dunno about the bolded ones. Let's assume Canon does move to a multi-layer sensor, and that the megapixel counts we've heard in the past are true. That puts the total photodiode count at 24*3 (if it's a three-layer sensor), or 24*5 (if it's their new five-layer sensor design, with the additional layers for dealing with facial spots and the like...I think this is unlikely, the five-layer sensor sounds like a studio camera thing, so would probably find it's way into the bigMP FF camera.) At 24*3, the total readable photodiode count (excluding DPAF) would be 72 million. If you factor in DPAF, that becomes 144 million.
Now, throw in the frame rate. At 14-bit, 72 million photodiodes is a total of 126megs of data PER FRAME. Actually, if we assume an increase of 7-10% in the pixel count for the masked border pixels, were actually talking about 77-79 million photodiodes, which comes out to 138.6meg of data PER FRAME. When we factor in a frame rate of 12fps, throw in some overhead, were talking about at least 1.7GB/s data throughput. Double that, for DPAF, and were talking about nearly 3.5GB/s data throughput for an AF read.
Dunno...the 1D X with dual DIGIC5+ gets 500MB/s data throughput in total. For Canon to jump from 500MB/s to 3.5GB/s in two years...seems far fetched to me.
So that means one of a few things. First, the "total" photodiode count could be around 24 million, which really means the sensor is a mere EIGHT MEGAPIXELS!! That's it! A measly 8mp! I have a hard time believing that, it doesn't make any sense. I think Sigma has done a grave disservice to Foveon by trying to upsell it as something it's not with their ludicrous megapixel counts...they have a 46megaphotodiode sensor in a 15megapixel camera. I at least hope Canon wouldn't stoop to the same misleading marketing for their own layered sensor.
So, if the camera isn't a measly 8mp APS-C sensor, then something else has to give. I could see Canon jumping from 500MB/s throughoput to ~1.5GB/s throughput. That seems more reasonable to me. In that case, I don't see DPAF being included, and the sensor megapixel count would probably be a little lower than 24mp.
The third option is simply that the sensor is NOT a layered sensor. The most likely option is that the sensor is 24mp bayer, with some kind of new and improved, more advanced, more accurate DPAF system that is tied into the same central AF logic that drives the lens from the dedicated PDAF unit (as per the recent patent that was posted here on CR.) That would be an improvement, it would certainly support 12fps (or more), although with DPAF, 12fps requires double the throughput. This still seems like the most likely option, though.
Still no information on whether Canon has moved to a better fabrication process, so who knows there.
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