Are bigger pixels less noisy?

Started 4 months ago | Discussions thread
Entropy512 Veteran Member • Posts: 5,234
Re: Are bigger pixels less noisy?
2

JahnG wrote:

Camera manufactors like Canon, Sony, (Panasonic) have made ”low noise” cameras with less and bigger ”pixels”. Do the manufactors not know what they are doing? (Some people in DPR say that such cameras are manufactored because the customers expect that sensors with bigger ””pixels” would be less noisy?)

Of note here: Despite carrying the "S" designation, you may notice that the majority of Sony's marketing for the A7SIII was not in regards to its capabilities at "nosebleed" ISO ratings, but in regards to its video capabilities.

That's because, when normalized to a given image size, PDR of most sensors has remained relatively constant for the past 5-6 years. There are some small variations, but not the huge improvements people remember seeing earlier in the development of digital cameras.

It used to be true that due to area on the sensor used for support circuitry, higher resolution sensors would have less "usable" light sensitive area - the pixels were smaller but the amount of space used by circuitry would not.

However we've advanced far enough that even vastly obsolete silicon fabs have feature size small enough to shrink that circuitry (for example, there's strong evidence the A6300 sensor is made on 45nm copper SOI - it hit market a year or so after Sony bought Yamagata TEC from Renesas and that facility was doing 45nm copper SOI, and the A6300 was the first Sony sensor marketed as using copper interconnects.  45nm copper SOI is vastly obsolete for other use cases.  A Chipworks article that is no longer available put Sony at around 180nm for the A7R and 250 for one 24MP A-mount FF sensor, and Canon at 500nm back in 2012) - in addition we have tricks such as backside illumination and (I believe Jim Kasson pointed this out a few years ago) gapless microlenses. These have allowed even high-resolution sensors to have high percentages of usable area.

You can't get past 100% which is, I believe, why we're seeing a plateau in PDR performance over the past few years:

https://www.photonstophotos.net/Charts/PDR.htm#Sony%20ILCE-7M3,Sony%20ILCE-7RM2,Sony%20ILCE-7RM3,Sony%20ILCE-7RM4,Sony%20ILCE-7S,Sony%20ILCE-7SM3

Note that there's another metric, EDR, which is per-pixel dynamic range - this will be worse for smaller pixels due to reduced area (per Eric's post), but in many cases, it's PDR that matters because normal people don't pixel-peep at 100%.

What is more important nowadays in the "is this sensor resolution too high?" discussion is in terms of throughput, readout rates, and bandwidth.  More pixels means either higher bandwidth/througput requirements to meet a given framerate requirement, or lower framerates given a fixed bandwidth/throughput limit (for example, pretty much anything with a Sony BIONZ X never showed evidence of exceeding more than about 500 million pixels per second sustained multiframe throughput, except the A7R4 which hit 600 - only a 20% improvement over many years.  We didn't see a major change until the A7SIII and A1 with the new BIONZ XR.)  This is why you still see video-oriented bodies (like the S) maintain low pixel counts - low pixel count lets them hit higher framerates and less rolling shutter.

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