Don said 'ISO setting control', and the ISO control does affect the conversion gain on cameras that have dual conversion gain, though not in a linear not standardised manner. Agreed that ISO is not conversion gain and that ISO setting isn't ISO.
March 29, 2023
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He did. I'm trying to make a point that it isn't ISO, to avoid confusion.
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Bob ,wouldnt the iso control operate the same as the electronic shutter ? because its using a timer to control the charging capacitor ?
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Currently, ISO control doesn't use a timer.
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- By AlanSh on April 10, 2023, 12:12 p.m..
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but it cant use anything else at pixel level (would be to complicated), just a simple transitor triggered to stop the charge to the capacitor ?
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That's wrong.
ISO "implementation" is a multi-stage chain, might even involve raw converter. In current consumer cameras it may involve pixel control, one or two variable gain amplifiers, ADC, multiplication in camera, multiplication in raw converter. In the current experimental implementations there are even more stages present, and architecture in some of those is quite different. -
It switches on/off an extra "capacitor" before the exposure starts.
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electronic shutter how does that control light exposure ?
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ISO settings influence the brightness after exposure - sometimes as analog amplification before the ADC, as in your example, or in the digital domain after the ADC (ISO implementation varies). At no time does ISO itself contribute to exposure.
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In the case of dual conversion gain it's an extra capacitor and a transistor that switches it in or out of circuit. Stopping the flow of charge to the capacitor would reduce photoelectron count, which is exactly the wrong thing to do.
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By the shutter speed I set or the camera sets to satisfy its meter.
Are there any sentences in my post you quoted that you think are not accurate?
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It doesn't work like that. Were it to it would be reducing the number of photoelectrons measured, which would result in the same effect as a smaller exposure - exactly what you don't want. The pixel circuitry contains an additional capacitor (the native 'capacitor' is the combined capacitance of the floating diffusion and source follower gate) and a transistor that can switch that capacitor in or out of circuit.
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It controls the time over which the sensor accepts light, as opposed to the time over which it is exposed to light. So, with a slight technicality it isn't quite controlling 'exposure time', rather 'integration time' - but it doesn't lead to conceptual problems if it's thought of as 'exposure time'.
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Boy, this thread has sure shifted away from the simple issue of whether "exposure" is how dark or light an image looks.
But in any case, different cameras have different implementations of ISO. It seems as if people are suggesting that all cameras do things the same way. That's clearly not the case.
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thats all i needed to win, on a slight technicality 😜😁
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i disagree , post a schematic that shows different. only extended iso is controlled digitally.
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Sorry, just not factual.
