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    • It's a limitation, or rather, just the characteristic of how signal processing works in photosensors. I'm probably going to butcher this explanation. It was explained a long time ago with awesome visuals, that I've long since lost. It goes something like this...

      When we clip highlights, what we see is the result of all the light wells (pixels) registering 1's. There's usually a pretty hard line cutting that off, because sensors exhibit strong clean signal strength going right up to its maximum capacity but will never register, for example, 1.001. But the black clipping is a softer number because it doesn't cut off sharply at 0.000. Before we get to 0.000 there is a bunch of line noise, that photogs think of as ISO, but engineers just think of as a increasingly muddy signal to noise ratio. Lifting the shadows amplifies the low signal and noise together, which means 1) there's lots of info down there that we can take advantage of...but 2) the more we rely on it, the more noise we introduce, which is why there's things look crappy if you try to lift extreme shadows w/o HDR techniques.