Originally posted by MossyRocks Well last summer Sony announced their 48MP sensor for cellphones and the pixel pitch there is already very close to the bottom end of red, pixel pitch of 800nm and the bottom of the red spectrum is around 700nm.
The issue is not whether or not one photon will ft into one pixel. The issue is, how many single photons will cross to more than one pixel. leading to cross talk. With one pixel being equivalent to one red photon, most of the photons will not be on a single pixel, and may just catch an edge, but the pixel will behave as its the photon hit right square in the middle when calculating the red value. This is a recipe for fuzziness that already affects K-1 and K-3 sensors. and is the reason Canon 5D 12 MP images still hold up today.
When deciding if CA is critical, Optical Limits use the "as long as the CA is less than .7 pixel it won't be noticeable" theory. With wavelength size pixels, one photon could easily energize 4 pixels. But here should be enough redundancy in the system that that 20% red photon doesn't affect IQ. And you do that by having enough photons directly hit the pixel to minimize the effect of the partial photons. Obviously, the larger the target, the more direct photon hits there will be, minimizing cross talk.
Looking at the Canon 51 MP FF sensor, there is some serious cross talk, leading to colour artifactiing, that is quite noticeable pixel peeping.
A sensor cannot differentiate what the light source doesn't differentiate. So, I'll be interested to see what the Sony sensor characteristics are, but I'm hardly going to grant them a free pass and say that will be a tool I'd consider using without some pretty extensive testing. I've also heard there are going to be Organic sensors with fantastic properties. I've been hearing it since 2012. Companies can say what they're working on, but that doesn't mean they'll ever get it done. Lets wait before we decide they are successful with their 48 MP cell phone sensor, until it's performance is tested.