If I’m going for the grainy retro look for some lowlight photos would it make sense to keep ISO low and add grain in post, or would the grain from turning up the ISO give a different kind of grainy look?
If I’m going for the grainy retro look for some lowlight photos would it make sense to keep ISO low and add grain in post, or would the grain from turning up the ISO give a different kind of grainy look?
Besides the information already posted here about noise and grain, I might have to add something to the way you seem to perceive ISO.
Increasing ISO while keeping the same light-conditions would rather decrease(!) your noise. There is a lot of misconceptions regarding ISO. The ISO (in digital photography) is simply working as a gain for your light, resulting in higher signal and noise levels. BUT, the noise you see is not dependend on how high your noise level is. It depends on how much more signal than noise you have. And as long as you don’t blow out your highlights, your signal to noise ratio stays the same. But if you shoot underexposed you decrease your signal to noise ratio and that’s why we think raising ISO adds noise. Because in that case we start using higher ISO and realize that we start seeing the noise. But compared to postproduction the camera still works with far more signal than in the resulting raw-file, meaning that increasing the ISO will introduce less noise than increasing the exposure of the Raw-file and shooting with high ISO results in less noise than increasing it in Post-Production.
Don’t believe me? Try capturing the same scene normally exposed with high ISO and than underexposed with low ISO and raise them to the same level of exposure in postproduction.