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when backing up my iPhone 14 ProRaw images to Amazon Photos through the iOS app, my 12MP raw DNG photos are only ~1 MB or so. However, on my phone they are closer to 20 MB. After downloading the uplaoded photo from Amazon Photos, the downloaded raw DNG is still only ~1 MB. This doesn't happen to the non-raw photos, i.e. live photos are about ~1 MB on my phone and on Amazon Photos.

By my understanding, Amazon Photos should be saving the full image.

  1. Am I losing quality here? Is there any way to check/quantify the quality loss?
  2. Anything I can do to prevent this, while still using Amazon Photos?

Thanks in advance!

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  • \$\begingroup\$ Are sure the files in Amazon photos are really DNG? \$\endgroup\$ Commented Nov 21, 2023 at 6:29
  • \$\begingroup\$ @RomeoNinov yea they are, I just checked again \$\endgroup\$
    – zli
    Commented Nov 22, 2023 at 8:20
  • \$\begingroup\$ Have you check if they are the same resolution, colour depth? \$\endgroup\$ Commented Nov 22, 2023 at 8:28
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    \$\begingroup\$ XN View MP have function to count unique colours in image. \$\endgroup\$ Commented Nov 22, 2023 at 11:58
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    \$\begingroup\$ @RomeoNinov tried that out. XN View MP thinks that the photo from Amazon Photos has gone through JPEG compression... 24 bits vs 48 bits from the raw image, and the format is JPEG TrueColor v1.1 vs APPLE. I suppose the Amazon Photos iOS app is compressing it before the upload... which is pretty annoying. Thank you so much for this tip!! Wonder if there's a way around that \$\endgroup\$
    – zli
    Commented Nov 22, 2023 at 19:22

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