I know, I know, it can be caused by various factors, like high ISO, poor lighting conditions, long exposure time, heat. (not that I know why the last two cause noise)
But where does noise REALLY come from? What is noise? What does it have to do with photons and photosites?
Noise is just miniscule variations caused by myriad of factors - heat, humidity, different amount of photons, properties of different electronic components, natural backround radiation etc. etc. etc…
And no… high ISO doesn’t cause noise, it just amplifies it.
This was a rabbit hole I went down recently that was quite illuminating.
Sensors have a native ISO and any extended (higher or lower) are simply the sensor amplifying or decreasing the signal.
No they do not. ISO is an output format (e.g. JPG) metric defined by ISO 12232 standard. It has nothing to do with image sensors.
Most cameras do change the operational parameters of the image sensor when the ISO setting is changed, typically the PGA (programmable gain amplifier) setting is changed and the signal is amplified the more the higher the camera’s ISO setting is.
That is not right.
Typically the ISO 100 (sometimes something else) setting on a camera is such that the image sensor is run at the lowest PGA amplification setting. Anything above that and the amplification is increased (and/or digital multiplication is used in software). The “extended lo” settings typically operate the sensor at the very same setting the ISO 100 does, just change the metering and processing of the data.
I think of it like trying to listen to a really quiet video or audio file on headphones or speakers. You can keep turning it up until you can hear what sounds are on that file. But you will also be turning up the background white noise
Life, uh, finds a way
No it doesn’t.
ISO setting is a lightness parameter. Adjusting it ajusts JPG lightnesss. This is very different from amplifying noise.
Regarding raw files and the underlaying information, the sensor tries to capture - using a high ISO does not amplify noise. Instead it on typical camera slightly reduces the little noise that the analogue to digital convenrsion adds, and some cases also reduces the noise that the pixel adds.
I appreciate your input, but instead of misinterpreting Wikipedia articles you should learn how electronics actually work. :)