Many thanks, guys! I was sleep while all this happened. So I am still digesting it. But From reading them once
I am not sure if I know the answer to my question. It was sort of a theoretical question but if you want example here is what made me ask this question although I has always been in my mind (slow mind
):
So, my theoretical question is: If I am a single pixel and I am correctly exposed, do I generate a lot of noise? And here is why this is a question for me: The background is also correctly exposed but at the expense of a longer exposure time. The foreground however is not exposed for more than the duration of the flash. So, I thought, and as Colin mentions, since that is the only choice sometimes to increase the ISO, that advice is based on the fact that theoretically where you get good light in the foreground or at the pixels that capture those areas, the noise issue is not as much of a problem as the background, regardless of what you can do in PP or with noise reduction softwares.
Am I being dumb and you guys already answered my question or no?
Cheers!