A major problem with blur beyond rounding errors, say due to the optics being somewhat blurry due to manufacturing difficulties and tradeoffs for weakening assembly tolerance requirements (like wanting rotationally symmetrical optical surfaces, despite a rectangular shaped actively-used image focal plane (e.g. CMOS photodiode array), and potential for specializing the design to evenly light up _just_ that rectangle), is that the photon shot noise has a standard deviation equal to the square root of the photon count.
A smartphone sensor pixel has space for some low 4 digits number of electrons (created with some probability from photons, but that stochastic effect doesn't matter for anything a normal user would photograph) and typically should have a fixed 2~10 electron standard deviation from the analog-to-digital-converter (well, mostly the amplifiers involved in that process).
So if your pixel is fully exposed at a high 10000 electrons, and you √ that, you have 100 electrons stddev from shot noise plus worst case 10 electrons stddev from the readout amplifier/ADC.
If you have a dark pixel that only got 100x less light to only have accumulated 100 electrons, √ of that gives 10 electrons stddev of shot noise plus the same 10 electrons stddev readout amplifier/ADC.
The problem is that while you have an SNR of 5 with the dark pixel, when trying to deconvolve it out of a nearby bright pixel, even perfectly with no rounding errors (1 electron = 1 ulp/lsb in a linear raw format), you now have 100/110 = 10/11 ≈ 0.91.
That's far worse than the 5 from before.
This gets worse if your ADC has only the 2 electrons stddev instead of the 10 (about 2x worse here).
That's the reason why deconvolution after the photon detector is a band aid that you only begrudgingly tend to accept.
The trade-off just requires massively increased aperture/light gathering, likely negating your savings on optics.
A smartphone sensor pixel has space for some low 4 digits number of electrons (created with some probability from photons, but that stochastic effect doesn't matter for anything a normal user would photograph) and typically should have a fixed 2~10 electron standard deviation from the analog-to-digital-converter (well, mostly the amplifiers involved in that process).
So if your pixel is fully exposed at a high 10000 electrons, and you √ that, you have 100 electrons stddev from shot noise plus worst case 10 electrons stddev from the readout amplifier/ADC. If you have a dark pixel that only got 100x less light to only have accumulated 100 electrons, √ of that gives 10 electrons stddev of shot noise plus the same 10 electrons stddev readout amplifier/ADC.
The problem is that while you have an SNR of 5 with the dark pixel, when trying to deconvolve it out of a nearby bright pixel, even perfectly with no rounding errors (1 electron = 1 ulp/lsb in a linear raw format), you now have 100/110 = 10/11 ≈ 0.91. That's far worse than the 5 from before. This gets worse if your ADC has only the 2 electrons stddev instead of the 10 (about 2x worse here).
That's the reason why deconvolution after the photon detector is a band aid that you only begrudgingly tend to accept.
The trade-off just requires massively increased aperture/light gathering, likely negating your savings on optics.