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What does "stack hundreds and hundreds of frames to bring out incredible detail" mean, technically?

all2 1y ago
There are algorithms in computational photography that effectively "stack" multiple images of the same thing in order to achieve a kind of 'super-resolution'. It's been a bit since I've done any of that, so I do not recall, but my hazy memory says its pretty straight forward linear algebra (and has the concomitant drawbacks that algorithms of this type have).
dredmorbius 1y ago
The 16 mm film format mentioned is usually a motion-picture, rather than still, camera format, generally shot at 24 frames per second (FPS), though values from 8 to 48 FPS were fairly common. Presumably the stacking was of 100s of frames would involve combining several seconds (8.33 seconds would be 200 frames of film at 24 FPS) to generate a higher-resolution image. Success would depend on how much camera and subject movement occurred over that time, though image stabilisation should help somewhat with the former. I suspect a clearer explanation of the process was omitted from the article, perhaps due to poor editing.
- dredmorbius 1y ago
  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.
procflora 1y ago
To take many exposures of the same scene and average the pixel values with the corresponding pixels from all the exposures. This increases the SNR and dynamic range, but naturally doesn't work very well if your subject isn't static. It doesn't increase the resolution of the image though. For the 16mm movie cameras in this case, they probably selected frames from rigidly mounted cameras with little subject motion to get a good result out of it. Glenn strapped in tight in his tiny cockpit probably provided them with a decent number of frames they could stack without introducing much motion blur. In fact, you can see a bit of blurring at the end of one of the white straps center frame in that shot: https://cdn.arstechnica.net/wp-content/uploads/2025/09/03b-Glenn-reentry_NASA_Andy-Saunders.jpg https://cdn.arstechnica.net/wp-content/uploads/2025/09/03b-G... It's a pretty common technique in astrophotography. Here's a page that goes into some more detail in that context: https://clarkvision.com/articles/image-stacking-methods/ https://clarkvision.com/articles/image-stacking-methods/

all2 1y ago

There are algorithms in computational photography that effectively "stack" multiple images of the same thing in order to achieve a kind of 'super-resolution'. It's been a bit since I've done any of that, so I do not recall, but my hazy memory says its pretty straight forward linear algebra (and has the concomitant drawbacks that algorithms of this type have).

dredmorbius 1y ago

The 16 mm film format mentioned is usually a motion-picture, rather than still, camera format, generally shot at 24 frames per second (FPS), though values from 8 to 48 FPS were fairly common. Presumably the stacking was of 100s of frames would involve combining several seconds (8.33 seconds would be 200 frames of film at 24 FPS) to generate a higher-resolution image. Success would depend on how much camera and subject movement occurred over that time, though image stabilisation should help somewhat with the former. I suspect a clearer explanation of the process was omitted from the article, perhaps due to poor editing.

dredmorbius 1y ago
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.

procflora 1y ago

To take many exposures of the same scene and average the pixel values with the corresponding pixels from all the exposures. This increases the SNR and dynamic range, but naturally doesn't work very well if your subject isn't static. It doesn't increase the resolution of the image though. For the 16mm movie cameras in this case, they probably selected frames from rigidly mounted cameras with little subject motion to get a good result out of it. Glenn strapped in tight in his tiny cockpit probably provided them with a decent number of frames they could stack without introducing much motion blur. In fact, you can see a bit of blurring at the end of one of the white straps center frame in that shot: https://cdn.arstechnica.net/wp-content/uploads/2025/09/03b-Glenn-reentry_NASA_Andy-Saunders.jpg https://cdn.arstechnica.net/wp-content/uploads/2025/09/03b-G... It's a pretty common technique in astrophotography. Here's a page that goes into some more detail in that context: https://clarkvision.com/articles/image-stacking-methods/ https://clarkvision.com/articles/image-stacking-methods/