This article should be read by everybody

Started Dec 12, 2013 | Discussions thread
K E Hoffman
K E Hoffman Veteran Member • Posts: 5,103
Re: Hard to bust the large vs small pixel myth
2

Nordstjernen wrote:

K E Hoffman wrote:

Yes you can't assume a higher res sensor will have more noise than another lower res camera or the previous model.. but it would have more than a sensor with the same design and larger photo reception sites.

The core of misconception:

K. E. Hoffman writes: " ... but it would have more than a sensor with the same design and larger photo reception sites."

No, the size/the numbers of photo reception sites does NOT affect the amount of noise for sensors of the same size! What matters is the light-gathering power of the sensor, that is the surface area, which is given by the physical size of the sensor.

So for a 12 Mp, 24 Mp and 36 Mp FF sensor the amount of digital noise will be more or less the same, but the characteristics of the noise might be a bit different.

The same would be true for a 12 Mp, 24 Mp and 36 Mp aps-c sensor.

You can't compare pixel by pixel. You have to compare pictures of the same size. Then the noise level will be almost identical, but the high res sensors will show more detail.

The main reason for this is better micro lenses with almost no gap between the photo sites and also much better noise reduction at the A/D level, before the raw files are written.

Yes the optimization of the light gathering surface is a key game changer.  Also the amount of sensor area below the lenses helps. General improvement in sensor sites so they function with less noise. Putting A/D converters closer to the sensor etc.  They all counteract the SNR issues with smaller and smaller light collection units.

That's why you can't compare sensors of different design and assume the pixel size on the Sensor will cause a predictable increase in noise  But same design with larger pixels means better SNR ...

Each sensor site has some natural noise in it.  If someone wants to show me that a larger sensor site has more noise that might be an equalizer.. BUT there are other places in the system that add noise.  The support circuits for each site.. circuit paths before the A/D converters.   Its like fixed costs in a business.. its there.  So when the light collecting ability goes down.. but the base system noise does not.. the SNR gets worse and it shows up when there is less light to collect.. thus we try to find a place to over expose but not blow out..

Noise does not happen at the SENSOR level.. it happens and the Sensor Site..

So if I take the same sensor area and double the resolution.. I cut the light going to each sensor site.. If I do not add in an improvement to lower noise or optimize light collected we get pixel more likely to have a reading that is not accurate.  At some point I might get to 100% efficiency all pixels hitting the lens get collected.  Then I cut the sensor size down.. I just get less light and I can only look at ways to reduce noise in the system.

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