ISO in digital cameras, is it handled physically, or in software?

[lassevk]

When reading and watching Youtube videos about ISO, they all say "amplify" or similar. I know that "amplifiers" is a physical thing, like in audio, but it could also be that all this is handled in software.

But, I assume this is not a software thing, because if it were, I would expect the raw file to just embed the ISO value separately, and then record the unamplified (unmultiplied?) data from the sensor, even though that could be an almost entirely black picture, ready to be handled by any software down the line, such as Lightroom.

So does this mean that ISO in digital cameras, such as Canon mirrorless camera, is handled using electronic circuits? I assume the actual pixel components of the sensor are analog in nature, so this could be a simple analog amplification circuit.

Does anyone (here) know how this is done?

 

[Rob2563]

When reading and watching Youtube videos about ISO, they all say "amplify" or similar. I know that "amplifiers" is a physical thing, like in audio, but it could also be that all this is handled in software.

But, I assume this is not a software thing, because if it were, I would expect the raw file to just embed the ISO value separately, and then record the unamplified (unmultiplied?) data from the sensor, even though that could be an almost entirely black picture, ready to be handled by any software down the line, such as Lightroom.

So does this mean that ISO in digital cameras, such as Canon mirrorless camera, is handled using electronic circuits? I assume the actual pixel components of the sensor are analog in nature, so this could be a simple analog amplification circuit.

Does anyone (here) know how this is done?

wow that is a very technical question but you tweaked my interest as a techie and I found this canon article that may answer some of your questions

Noise reduction options explained

How can you shoot cleaner still images and video in low light? Canon experts explain the latest Canon EOS and Cinema EOS noise reduction technologies and functions.

www.canon.co.uk

 

[PB Aus]

Hi...all photosites on the sensor have an analogue amplifier which applies gain or amplification of the light captured by the sensor. That amplification based on the iso setting selected. The sensor sensitivity does not alter. After amplification the signal then passes to the ADC - analogue to digital converter. So the amplification takes place prior to conversion to digital. Importantly the amplification is not letting more light onto the sensor, it's electronically altering the signal strength.

 

[lassevk]

Hi...all photosites on the sensor have an analogue amplifier which applies gain or amplification of the light captured by the sensor. That amplification based on the iso setting selected. The sensor sensitivity does not alter. After amplification the signal then passes to the ADC - analogue to digital converter. So the amplification takes place prior to conversion to digital. Importantly the amplification is not letting more light onto the sensor, it's electronically altering the signal strength.

Thanks, so it's an analog amplifier built into the individual sensor pixels (/pixel sensors?).

 

[lassevk]

wow that is a very technical question but you tweaked my interest as a techie and I found this canon article that may answer some of your questions

Noise reduction options explained

How can you shoot cleaner still images and video in low light? Canon experts explain the latest Canon EOS and Cinema EOS noise reduction technologies and functions.

www.canon.co.uk

While this was a good article, I don't feel like it particularly answered my question.

It did explain how the camera copes with noise though, but it didn't really touch upon how ISO really affects the outcome.

 

[PB Aus]

Each photosites on the sensor yes ...it's not a pixel until it's converted to digital

 

[lassevk]

Each photosites on the sensor yes ...it's not a pixel until it's converted to digital

Got it. Thanks!

 

[PB Aus]

Harvard University Photography Course

Exposing Digital Photography is a free photography course from Harvard University and is available online. The digital photography course includes 24 hours of instruction.

photographycourse.net

There are many sources of information as you say in your original post. You could also check out the link above. ....PB

 

[CrashPC_cz]

Heya. ISO speed handling is an internal thing that manufacturers don't want to discuss. Maybe competition is listening.

It is handled on both hardware and software side. Simple multiplication doesn't work well, because digital processing has its limits, even based in the hardware. Signal from the camera sensor is quite weak (think of few photons/electrons, that don't do much). And so amplification at or near sensor level is best, for best noise performance. Not just raw sensor performance, but for the camera to handle the signal as good as possible. Higher voltages than what sensor produces upon its excitation/exposure help with this tremendously.

While we know the general technology, we often do not know for sure, what is the secret sauce of each manufacturer.

Though this knowledge would be inconsequential to us anyways. There is nothing much at all we can do with it, and so we measure it and use it to our best abilities.

That's where dynamic range and exposure lattitude tests come in. We see that we are better off with higher ISO speeds on maximum exposure compared to postprocessing brightening. On certain occassions, I can shoot fair ISO 25600 image on APS-C sensor with not much of a quality distractions. Not possible at ISO100 with the same exposure settings. It would 1) look pitch black upon composition/exposure, and 2) would show much more noise, rendering the image unusable. Definitely use your ISO speed settings to fill the histogram.