I could not read TFA since it was in Japanese. From Amazon.com's pages:
About Prime Photos: http://www.amazon.com/gp/help/...
In addition to the unlimited photo storage, you will also receive 5 GB of free storage space that can be used to store videos and files we canâ(TM)t recognize as photos.
Certain photo formats are excluded. For more information, go to Cloud Drive Photos & Videos File Requirements.
So apparently they decide what is a photo. Myself I'd not trust a third party to not degrade the quality; I'd opt for encrypted container with photos INSIDE it. The same page also restricts this to "personal use":
Prime Photos is for your personal, non-commercial use only. You may not use it in connection with a professional photography business or other commercial service.
Personally I think that sucks. By comparision, my VPS provider gives me a very cheap VPS which I can use for whatever purpose I want as long as I do not break any laws or disrupt other users. They price based on performance and bandwidth; not arbitrarily created market segmentations.
Cloud Drive Photos & Videos File Requirements: http://www.amazon.com/gp/help/...
Photos and videos you upload through your web browser on the Cloud Drive website must be 2GB in size or less.
File and folder names must contain less than 255 characters, and cannot include the incompatible characters listed below.
They list common supported formats; this includes RAW. And they do mention encryption:
For photos: JPEG, BMP, PNG and most TIFF files (these files typically have the .jpg, .jpeg, .bmp, .png or .tiff extensions). In addition, some RAW format photos can also be viewed. For more information, go to About RAW Photo Files.
For videos: MP4, Quicktime, AVI, MTS, MPG, ASF, WMV, Flash and OGG.
Note: The unlimited photos storage benefit for Prime members only applies to files recognized as photo files. Photo files that have been encrypted before they're uploaded will count against your storage quota.
About RAW Photo Files: http://www.amazon.com/gp/help/...
Nikon (NEF files) - Nikon D1, Nikon D1X, Nikon D4, Nikon Coolpix A, Nikon E5700, Nikon AW1, Nikon D800, Nikon D50, Nikon D610
Canon (CR2 Files**) - Canon 5D, Canon 1D, Canon 1D MarkIIN, Canon Rebel SL1, Canon 60D, Canon 5D MarkIII, Canon 1D MarkIV
**While Cloud Drive recognizes these files as photos, some of the information associated the file (like the time and date the photo was taken) may not be recognized.
Sony (ARW files) - Sony A7, Sony A7R, Sony A6000, Sony NEX-5T, Sony NEX-3N, Sony NEX-6
I doubt RAW format pictures can be compressed lossily? Does anyone know this for a fact?