Editing Talk:1551: Pluto
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.jpeg compression only produces those artifacts on digital images. It was designed for professional photographers and did not take into account the effects of hard edges in the image since film images have no hard edges! It just got adopted by everybody else early on so we're stuck with it even though it can work very poorly on digital images. [[User:ExternalMonolog|ExternalMonolog]] ([[User talk:ExternalMonolog|talk]]) 17:30, 15 July 2015 (UTC) | .jpeg compression only produces those artifacts on digital images. It was designed for professional photographers and did not take into account the effects of hard edges in the image since film images have no hard edges! It just got adopted by everybody else early on so we're stuck with it even though it can work very poorly on digital images. [[User:ExternalMonolog|ExternalMonolog]] ([[User talk:ExternalMonolog|talk]]) 17:30, 15 July 2015 (UTC) | ||
| β | :That's... interestingly not-quite-correct. The JPEG/JFIF method is a good-but-lossy version of digital image compression that outperforms (on compression terms) non-lossy methods of defining a digital image but doesn't work well with hard-edges. Photographs taken in digital format, or converted into digital format from a 'analogue' original, are often put through lossy compression because (for a wise amount of 'loss') the artefacts are easily lost in the already noisy and flowing 'real life' image details, just like the compression of MP3 (MPEG3 Audio Layer, or whichever related standard) applied to audio loses some detail but is generally drowned out by what 'remains', to the casual listener. (Images like graphs and diagrams are ''replete'' with hard edges, and have far fewer needs for subtleties of shade, so using the non-lossless PNG or even GIF (now that it's out of copyright, if that was ever your | + | :That's... interestingly not-quite-correct. The JPEG/JFIF method is a good-but-lossy version of digital image compression that outperforms (on compression terms) non-lossy methods of defining a digital image but doesn't work well with hard-edges. Photographs taken in digital format, or converted into digital format from a 'analogue' original, are often put through lossy compression because (for a wise amount of 'loss') the artefacts are easily lost in the already noisy and flowing 'real life' image details, just like the compression of MP3 (MPEG3 Audio Layer, or whichever related standard) applied to audio loses some detail but is generally drowned out by what 'remains', to the casual listener. (Images like graphs and diagrams are ''replete'' with hard edges, and have far fewer needs for subtleties of shade, so using the non-lossless PNG or even GIF (now that it's out of copyright, if that was ever your concerned) would be better... Depends on whether you want need more than 256 different colours or a humorous animation. If you want both, there are also solutions, but that's the usual decision I'd be making.) |
:I doubt that NASA uses .JPG images (at least between spacecraft and ground, although maybe for later web publication). There would probably be a (non-lossy) compression scheme (either inherently in the format of the image, or of the 'raw' image consisting of original arrays of bitplains, just to cut down on transmission time), so that as much exact science as possible could be extracted from the original pixels without 'smearing' and such artefacts. Professional (terrestrial!) photographers will often take RAW images (instead of/alongside the quick-and-dirty JPEG ones), for better quality (and no-artefact) images that might end up being blown up to poster-sized images, or from which a small segment will be blown up (e.g. ground-based amateur astronomical photography), that would otherwise so easily reveal the flaws. | :I doubt that NASA uses .JPG images (at least between spacecraft and ground, although maybe for later web publication). There would probably be a (non-lossy) compression scheme (either inherently in the format of the image, or of the 'raw' image consisting of original arrays of bitplains, just to cut down on transmission time), so that as much exact science as possible could be extracted from the original pixels without 'smearing' and such artefacts. Professional (terrestrial!) photographers will often take RAW images (instead of/alongside the quick-and-dirty JPEG ones), for better quality (and no-artefact) images that might end up being blown up to poster-sized images, or from which a small segment will be blown up (e.g. ground-based amateur astronomical photography), that would otherwise so easily reveal the flaws. | ||
:Also, IIRC, recent Pluto pictures had notably been created by NASA based upon high-resolution monochrome and lower-resolution colour images from two cameras (usefully analysed seperately, in their own right, and doubtless also needing different exposure times to create) combined together to create the headline pictures we've been seeing. | :Also, IIRC, recent Pluto pictures had notably been created by NASA based upon high-resolution monochrome and lower-resolution colour images from two cameras (usefully analysed seperately, in their own right, and doubtless also needing different exposure times to create) combined together to create the headline pictures we've been seeing. | ||
| β | :Incidentally, noticable JPEG artefacts tend to be 8x8 pixel regions (most often seen when a small photographic region is digitally | + | :Incidentally, noticable JPEG artefacts tend to be 8x8 pixel regions (most often seen when a small photographic region is digitally . For those that need them, there are "artefact removal" tools in most decent image editing programmes that (with practice) can 'reverse' (or, rather, 'blend') the more obvious artefacts, after the fact. I suspect Randall's image's 'artefacts' are a selectively edited 'artefact addition' (easily done, with the likes of Photoshop and GIMP, and related to 'pixelating' method used to selectively obscure detail) on the original image. NASA never had to 'clean' the image, although some of its released images may have been 'dirtied' after down-conversion. [[Special:Contributions/141.101.98.166|141.101.98.166]] 20:51, 15 July 2015 (UTC) |
One of a number of pareidolic features Randall has outlined. [[Special:Contributions/108.162.212.4|108.162.212.4]] 20:56, 15 July 2015 (UTC) | One of a number of pareidolic features Randall has outlined. [[Special:Contributions/108.162.212.4|108.162.212.4]] 20:56, 15 July 2015 (UTC) | ||
