Are bigger pixels less noisy?

Started 4 months ago | Discussions thread
Entropy512 Veteran Member • Posts: 5,220
Re: Are bigger pixels less noisy?

JahnG wrote:

Entropy512 wrote:

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:,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.

Thank you very much for thoroughly commenting on that part of my original post.



No problem.  As one example of a case where a high-resolution sensor had penalties:

The Sony A7III can stay below that 500 MPixel/sec limit when oversampling the full sensor width for video at a 16:9 crop.  It's 6000 pixels wide, so a 16:9 crop is 6000*3375

6000*3375*25 = just a hair over 500 MPixels/sec

Bump that up to 7952 pixels wide (R3) and you're at almost 900 MPixels/sec, which is above even the R4's documented/known capability for multiframe sustained rates  (Note that JimK has measured single-frame readout rates much higher than this, but I don't think anyone has found any evidence of these rates being hit for sustained multiframe operations) - and, not surprisingly, the R2, R3, and R4 all either lineskip or bin when in full sensor width video modes.  (Not sure which, but either way, they sacrifice quality to fit within a bandwidth limitation.)

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