File format for print?
There are 16 bit jpegs, but I haven't seen any software that can create them. You can do any color space you want, but it will be 8 bit. The 16 bits is mostly a requirement for editing, not printing. If you do ProPhoto RGB, I would make sure they can handle it.
Do you have any colors in the image that aren't in AdobeRGB or sRGB?
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