> For example, by stitching together multiple dark images to try to make a brighter one. (Dedicated cameras tend to have better-quality but conceptually similar options like long exposures with physical IS.) However, we are starting to introduce the core sin of modern computational photography: imposing a prior on the image contents. In particular, when we do something like stitch multiple images together, we are making an assumption: the contents of the image have moved only in a predictable way in between frames. If you’re taking a picture of a dark subject that is also moving multiple pixels per frame, the camera can’t just straightforwardly stitch the photos together - it has to either make some assumptions about what the subject is doing, or accept a blurry image.
This applies to dedicated cameras too though - physical image stabilization can compensate for camera motion but not for subject motion. The difference is that a) physical IS can compensate throughout each exposure, not just between exposure and b) the photographer is not bound to a black box algorithm but can instead use his own a priori knowledge to align the images if needed.
Yes, I meant to imply that dedicated cameras are committing the same "sin" here. I only meant physical IS is better because you don't need to do things like periodically read out the sensor. You are getting a true full-duration exposure that won't produce artifacts like tearing or skips.
The iPhone has physical IS too. It's very good. (Image stabilisation tends to work better for smaller sensors, as you have less weight to move around and less far to move.)
>In particular, when we do something like stitch multiple images together, we are making an assumption: the contents of the image have moved only in a predictable way in between frames
From this way of looking at things a normal long exposure also imposes a prior assumption (that nothing is moving). It's just that we're used to the artefact that's generated when this prior isn't true (motion blur).
This applies to dedicated cameras too though - physical image stabilization can compensate for camera motion but not for subject motion. The difference is that a) physical IS can compensate throughout each exposure, not just between exposure and b) the photographer is not bound to a black box algorithm but can instead use his own a priori knowledge to align the images if needed.