this post was submitted on 24 Oct 2023
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Iso causes noise. Stop spewing the Bs northrup Invents.
Ultra bright outdoors, shoot at 1/4000 f22 iso 26000 it will be noisy. And don't give me the "1/4000 f22 makes little light hit the sensor, it's lack of light"
Lack of light makes you use high iso to expose correctly, therefore noise. Of course.
Oh for crying out loud.
Difficulty: He didn't invent that, he literally parroted it.
OK - I won't.
Little green men from Mars caused the noise!
OR... it could just be Signal vs Noise and if you do not have enough signal you will have noise... and all the signal you will ever have is gathered before ISO is applied.
Thus it is proved - all the noise is also gathered before ISO is applied.
You realize you just reversed your position, right? Lack of light does indeed force you to use high ISO, and that lets you see the noise that was already there.
Use that same low light scenario. Shoot at iso 100. And you get a perfectly clean black exposure.
See, low light, no noise. So low light doesn't equal noise.
Boosting iso to get the exposure right when there is a lack of light. Does, as you expose the noise too
I wasn't going to get involved in this one as well but here we go.
In this scenario, if you kept the ISO at 100 but instead of increasing ISO, you kept the shutter open for longer, you will also get a perfectly exposed image with minimal noise. If noise was inherent to low light scenarios, you would be capturing more of it because your sensor would be exposed to that noise for longer, but that's not the case.
And yes, you would still get a small amount of noise (and hot pixels), but that's thermal noise from keeping the photovoltaic sensors exited for a longer period of time.
From an electrical engineering perspective, you’re both right.
ISO in digital sensors is an amplification of the analog signal output by the photovoltaic sensor before it is converted to digital. Amplifiers indiscriminately amplify both noise and your signal of interest. In that sense, he’s right that a high quality sensor with little inherent noise will produce a less noisy image at high ISO than a low quality sensor with a lot of inherent noise. A high ISO (amplification) will serve to amplify noise existing in your signal.
However, amplifiers also have a quality known as “noise figure”, in that all non-ideal amplifiers will add some noise to a signal. So you are also right in that there is some amplifier added noise that is possibly more visible when you increase your ISO, because amplification tends to reduce your maximum theoretical dynamic range through the additive noise, not increase it.
All that being said, this is all semantics and in practice I think the comment you’re replying to is correct, but is a bit loose with some technical concepts that don’t really matter in practice.