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I often read that larger photosites have better SNR performance. However, from further reading and test footage I have seen. It seems that, as many people also rightfully point out, it has more to do with the total area of the sensor / sensor used. So I would assume that two sensor with similar sizes, but the one with the larger photosites and hence lower pixel count, would have the same amount of Noise as the latter sensor, with smaller pixels and a higher pixel count.

This brought me to the question: “what the benefit of larger pixels are?” From what I know and also relating to my last post, I would assume it is that:

1.It’s easier to resolve the individual pixels, e.g. not as affected by diffraction and doesn’t require a lens with as high of a spatial resolution

  1. Probably the main component, being its ability to have a higher full well saturation point, leading to an increased dynamic range.

Is this correct or am I missing or confusing something ?

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    \$\begingroup\$ Larger pixels have less noise per pixel, though you are mostly right about the overall image noise, unless you crop. \$\endgroup\$
    – dandavis
    Commented Nov 29, 2023 at 5:10

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There is no significant benefit to larger photosites from a user standpoint.

  1. It is easier to resolve to the level of a larger photosite, but that is somewhat irrelevant... i.e. using more pixels than necessary to record a detail doesn't reduce it's sharpness/resolution. And regardless of the lens' IQ there is almost always an increase in recorded resolution with an increase of sensor resolution due to increased oversampling; it's just usually far less than the the increased sensor resolution would suggest. E.g. 17MP for a 25MP D750 vs 20MP for a 46MP D850 with the Nikon 80-400G lens.

It is the fact that most lenses do not resolve to the level of the sensor that allows for the removal of the anti aliasing filter without it being terribly problematic. That allows for greater sharpness of the details which are resolved. And increased sampling also increases color accuracy.

  1. As a stand-alone consideration, larger photosites do have a larger FWC and greater dynamic range potential; but that is also largely irrelevant. When there are more photosites of smaller size each photosite gets less of the total. I.e. for the same exposure and DR smaller photosites require less capacity.

The opposite is that smaller photosites have a higher conversion gain... i.e. they are actually more reactive to light and require less light to generate useful data. They extend the dynamic range by being able to record farther into the darks. This is why dual gain sensors are becoming common... a larger FWC at low ISO's, and a smaller FWC for higher ISO's (darker situations).

However, it is quite possible that one would not notably benefit from higher sensor resolution due to technique/situations/etc. And one could say that the reduced file size a lower resolution sensor generates are an advantage in some ways (processing/storage/etc).

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    \$\begingroup\$ photosites potential to capture a higher dynamic range. I guess there are a bunch of other factors I am ignoring and the whole engineering behind the sensor. I just feel like from all I've heard, the quality of the Lens seems to really be the bottleneck in the equation, rendering the immense pixel counts of some smaller sensors almost vain or at least inferior, in comparison to Dynamic range and noise performance. However I guess you did mention that smaller photosites can lead to increased dynamic range as well. \$\endgroup\$
    – vannira
    Commented Nov 27, 2023 at 19:11
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    \$\begingroup\$ @vannira, if you use two sensors of differing resolution to record the same scene the exposure settings required are the same for both. And any highlight clipping will occur at the same time in the same areas. I.e. what matters is light/area. Smaller photosites divide the light up between more of them, so there is no loss in recordable DR capability. Instead there may be an increase in DR capability due to the higher conversion gain of smaller photosites. E.g. the 16MP Nikon D4 has a photographic DR of 10.4 EV where the 46MP D850's is 11.6 EV. \$\endgroup\$ Commented Nov 27, 2023 at 20:30
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    \$\begingroup\$ In regards to recorded resolution; in theory it would only take 64 photosites to record a checkerboard. But for that to happen the two would have to align perfectly, and that's not likely to happen. So having more photosites than required (oversampling) improves accuracy and the likelihood a detail will be resolved. There is a limit to the benefit of increased oversampling, but most half decent lenses are resolving enough that even at higher sensor resolutions details may be missed. \$\endgroup\$ Commented Nov 27, 2023 at 20:37
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    \$\begingroup\$ @vannira, Some things depend on the technology involved/employed... Early on more pixels meant more gaps between the microlenses; but now they all use gapless microlens arrays. And if it is a front illuminated sensor, more pixels means more circuitry before the pixels the light has to be focused past/between; but now we have backside illuminated sensors with the circuitry behind the photosites. And they do make 6k sensors... my current Nikon Z9 is 8k. But, if you are not making full use of that resolution (settings/situation/technique/etc) then there's no/little benefit either. \$\endgroup\$ Commented Nov 28, 2023 at 22:59
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    \$\begingroup\$ Not necessarily. Larger photosites will be better for larger details and higher contrast. But larger photosites cannot even see/record smaller details; they combine as one within the larger photosite. \$\endgroup\$ Commented Nov 29, 2023 at 13:55

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