Photographing the Milky Way

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Lossless Compression
lɔ́slɛ́s kəmprɛ́ʃən
When images are recorded to a camera's memory card, or saved on a computer, the file can be stored in either an uncompressed or compressed format. However within the compressed format there are often two or more options for compression: lossless and lossy. With lossless file compression, the algorithm used to compress data can compress and uncompress data infinitely without any visible image data being lost. Lossy compression, on the other hand, will visibly degrade the file's image quality each time it is saved. If you were to save a JPEG image, open it again, and then save it again, and then repeat this process a number of times, you would see noticeable image deterioration throughout the procedure. For this reason, lossless compression is useful when it is expected that a file will be worked with repeatedly. RAW and TIF examples of file types that can use lossless compression, whereas the common JPG file type has no lossless compression option.