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As you increase the gain you decrease the read noise with CMOS sensors. This means that for the same exposure time you’ll get less noisy images... because the read noise is lower.
You used the example of 30s images in previous posts, at low gain you may not be getting even close to being read noise limited which will severely damage low signal areas. With 30s exposures at unity, the read noise is lower and that may not be an issue. This just means that with lower gains you need longer exposures to get above the noise floor.
Also, being below unity never means that you’re losing dynamic range. If you have a well depth of 60k with a 14-bit ADC you’re not losing dynamic range. The ADU is an Analog to Digital Converter as you’re well aware from radio applications, all you’re doing is changing it from a physical to a digital format. You’re never losing the range by cramming it from 60k to 16k simply because all of the forms of noise are scaled down as well.
This gets back to what I was saying a few posts back about what dynamic range is, it’s the amount of discrete bits. If your camera only has 12 bits worth of dynamic range ON SENSOR then whether it is a 14-bit or 16-bit ADC doesn’t matter because the other 2-4 bits is just noise error and padding.
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