willie_901
Veteran
Impossible.
Camera ISO setting is not exposure. Camera ISO does not change sensor sensitivity.[1]
Increasing camera ISO amplifies the rendered image brightness after the shutter closes.
The goal is to render with an acceptable brightness level when the light meter estimates a shutter and, or aperture time that produces underexposure when the shutter is open.
Practical rendered image brightness is achieved by increasing the analog signal gain identically for all for photo sites before these data are digitized. Most cameras supplement electronic gain increases with in-camera multiplication of raw file digital numbers. At very high camera ISO setting increasing analog signal gain is no longer useful. Higher ISO settings increase the in-camera raw file number values using digital multiplication.
This means one can create ISO 3.28 million when rendering using any camera's raw file. The issue is the the rendering aesthetic.
1. Some cameras use dual conversion-gain sensor technology. Now the sensor photosites' gain does increase by one to two stops when the camera ISO setting is set above 400 to 800. Different brands use different dual conversion-gain strategies.