Wish lists are great, but this is one where the technicalities matter.
The middle one could not pixel-binned RAW, even in quotes. It could be “RAW” like mRAW and sRAW. Binning two pixels would give distorted output, either 3:1 or 3:4 aspect ratio depending on the binning direction.
Even binning four pixels is complicated, because if you bin adjacent pixels you must demosaic at that time (i.e., it’s not RAW after binning), or use a quad-Bayer CFA. The latter is the approach taken by OM-1 and by Apple in the iPhone 14 Pro main camera (sensors made by Sony)
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That’s a great approach when the main application is the binned output. The OM-1 is sold as a 20 MP camera, though it has 80 million photodiodes. Likewise the default iPhone 14 Pro main camera output is 12 MP (matching the 12 MP sensors in the other two cameras), it only outputs 48 MP in RAW.
The ‘problems’ with the quad-Bayer array are spatial and color resolution when outputting the full MP count. The four pixels of each color block (in Sony’s implementation) are under a single microlens, so the non-binned output is closer to the binned output in terms of real resolution – e.g., using the OM-1 in high resolution mode (80 MP output) gives a spatial resolution above 20 MP, but closer to that than to 80 MP. Color resolution of the full MP output is also lower than the standard CFA because each color block is further apart, meaning a greater magnitude of color interpolation.
OTOH, the OM-1 leverages those four pixels under one microlens in a similar manner to the two sub-pixels under one microlens used by Canon for DPAF, giving the OM-1 quad-pixel AF i.e. every pixel in the 20 MP array functions as a diagonal cross-type AF point.
I’m not sure how Canon will choose to implement binned output, if they do so at all…
Will they use a Sony-type solution with a quad-Bayer CFA and QPAF (they patented horizontal-vertical that differs from Sony’s diagonal) but functions best for binned output?
Or a true high MP sensor with one microlens per pixel, with either four subpixels or alternating orientations of dual subpixels for cross-type AF, and the binned output would be demosaiced and thus not RAW?
Or a middle-ground approach such as a quad-Bayer array with each pixel having its own microlens and alternating DPAF, enabling full MP spatial resolution while sacrificing some color resolution for a true RAW 4-pixel binned output?
Time will tell, but it’s important to keep in mind that, “90 MP RAW with 22.5 pixel binned ’RAW’,” is more involved than simply combining blocks of four pixels.