NavList:

Lu, you wrote:
"That's because the JPEG algorithm reduces that amount of data that needs to be stored by (in layman's terms) saying "this pixel is very like the one next to it, so I'll just store the differences" -- with said differences typically requiring many fewer bits than repeating the entire new pixel."

Not really. The process you have described, storing the difference, is a "lossless" compression algorithm since EXACTLY the same pixel information can be recovered by "undoing" that process. By contrast, the JPEG algorithm is normally "lossy" and throws away large amounts of image information that are not readily visible to a normal observer. And of course that algotithm is "tunable" so that you can dial in just the right trade-off between compression (from throwing away more image information) and quality. Raw files are different from both of these extremes. They are device-specific, proprietary formats that often include more information than a normal lossless image requires. The size can vary even without losing image information.

This is really off-topic, so let's wind it down. For Greg, I would just say "google it" (try "natural language" searches --they work really well these days). The big difference between the world of Windows software on a relatively new machine and Mac software on a relatively old machine is that there is a HUNDRED TIMES more of the former than the latter written by an eclectic mix of professional software developers (e.g. Adobe), highly skilled semi-professionals (e.g. Irfanview), and hobbyists with skill levels all over the map. You can find just the right tool out there somewhere and just the right plugin for Irfanview or whatever software you adopt as your favorite. By the way, it can be useful to look for big review articles and also Wikipedia articles that compare products in a given category. You have far more to choose from, and that's good news, but it does take time to dig through it all.

-FER

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