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On Sun, Apr 28, 2013 at 2:43 AM, Kyle Banerjee <[log in to unmask]>wrote: Every choice people make is about loss. Equipment, optics, lighting, > you name it. But for some reason, the instant we're talking about bits of > data > on a disk, people plan as though capacity were unlimited when most > archives are severely underresourced. > Strictly speaking, it is not correct to say that every choice is about loss (or cost), and for once I'm saying this in a case where the difference is actually significant. [Someone help edsu to the fainting couch.] If a particular set of choices are below the Production Possibility Frontier<http://en.wikipedia.org/wiki/Production%E2%80%93possibility_frontier>, then those choices are strictly inferior to those that are on the Frontier. Why is this relevant? Because, for the situation where lossless image storage has a very value, TIFF is not the most space efficient way of storing the data. A month or so ago I did a few measurements, using a (not necessarily representative) color photograph (TIFF extracted from a Canon EOS-10D raw). For lossless conversion, I used uncompressed TIFF, compressed TIFF, PNG, and JP2 (100% quality). Measurements using the ImageMagick "compare" utility confirmed zero signal loss: -rw-r--r--@ 1 ses staff 18M Mar 19 14:52 CRW_4237_tiff_8_uncompressed.tif -rw-r--r--@ 1 ses staff 9.4M Mar 19 14:53 CRW_4237_tiff_8_compressed.tif -rw-r--r-- 1 ses staff 8.2M Mar 19 14:29 CRW_4237-0.png -rw-r--r--@ 1 ses staff 6.1M Mar 19 14:03 CRW_4237_quality_100-0.jp2 For lossy compression, using RMSE as the metric, we can see that JPEG at 90% quality is showing measurable signal degradation, with a compression ratio of 4.7:1 relative to the JP2 file (vs. 14:1 relative to uncompressed tiff, and 7.2:1 for compressed). $compare ... CRW_4237_jpg_90.jpg = 459.806 (0.00701619) [1.3M] (4.7:1) JP2 at quality 75 showed slightly less signal loss by RMSE, with a compression ratio of 5.5 : 1 $compare ... CRW_4237_quality_75.jp2 = 457.959 (0.006988) [1.1M] (5.5:1) Note that the image type was a color photograph; other image types may get better lossless compression using PNG or TIFF. Also, some people have expressed concern over the use of JP2 for archival purposes due to a relatively small number of open-source libraries. On the other hand, JP2 has some potentially useful properties for distributed replicated preservation (layers with fine levels of detail could be split off and stored on fewer replicas). Simon