Oh, and "image stacking" is the technique of combining multiple images within a single frame, allowing for greater clarity (as in here), removing noise (frequen

Oh, and "image stacking" is the technique of combining multiple images within a single frame, allowing for greater clarity (as in here), removing noise (frequently applied in astrophotography), or depth-of-field / focal-plane stacking. This almost always implies digital image processing, and depending on the goal / intent, various filters or masks may be applied. De-noising typically relies on including only visual elements appearing in most (but not all) frames of the stack, eliminating glitches such as satellite flares, meteors, terrestrial-based light sources, aircraft, sensor noise, or even radiation spots. "Take Better Night Sky Photos with Image Stacking" <https://photographylife.com/night-sky-image-stacking https://photographylife.com/night-sky-image-stacking> "Focus Stacking" (Wikipedia) <https://en.wikipedia.org/wiki/Focus_stacking https://en.wikipedia.org/wiki/Focus_stacking> Again, from TFA the source was motion-film footage from fixed-position cameras which could be used to generate images with much greater resolution than any individual frame. Note that 16mm film grain is typically fairly large, but with stacking and post-processing, smaller details can be inferred.