So I am going to nerd out here for a bit 
I had read somewhere that the recent Sony cameras are ISO invariant. Meaning the raw data captured by the sensor doesn’t depend on what ISO is set in the settings. So if you shoot a photo at 3200 ISO in the camera and compare it with the same photo shot at 320 ISO and then later brightened in software, you would notice no difference.So a couple of months ago when I was at the Grand Canyon in Arizona, I decided to try it out. Finally got around to pixel peeping on that.
On the left is what I would normally shoot at night, at 3200 ISO, a 15s exposure. On the right, I reduced the ISO down to 320 with everything else the same. And now I added exposure via software. And indeed, the noise introduced by the camera when I bump up the ISO on it is at the same level if I add exposure in post processing in software.
So why would I do this? What did I gain by shooting at low ISO? One thing is that if I had accidentally set my ISO too high, I couldn’t have dialed it down in post. So for sure, on sensors like this, it seems to be a good strategy to underexpose when in doubt.
And that points to the related advantage, if I have the moon in this photo, or the lights on the north rim as can be seen in this picture, those lights don’t get blown out at the low ISO. So I can extract slightly better dynamic range in post-processing on photos that are shot at lower ISO.The limitation to shooting at base ISO and brightening later, however, is that I was only seeing a black preview on the back of my LCD all night! I usually shoot without post-processing in mind, I don’t have time. I prefer to get all the settings right, so I can quickly get it out without additional steps. My bias has been speed over quality. So not sure if this is for me. But it is exciting to finally verify for myself that ISO invariance is a thing, and it’s kinda fascinating. Anyone else who has experience with this?
