ISO invariance is a topic that wasn’t really something that most people considered until recently. At least, not unless you were into certain speciality fields like astrophotography. But what exactly is ISO invariance? Well, the over-simplified answer is that your images look the same regardless of whether you boost the ISO in-camera or in your exposure in post.
In reality, it’s a little bit more complex than that, and the implications of whether or not your camera is ISO invariant can have a big impact on how you shoot and what settings you choose to shoot at. But this deep dive from astrophotographer Alyn Wallace goes into great detail on exactly what ISO invariance is and how it can impact your photography.