...You would now think you can stream your whole library on that computer. Nope... you open it up and all it streams is the same folders you selected to sync with it. Which doesn't work well with me when I border on 20,000 + photos and don't want to sync that to my TV hard drive.
Remember that photos have the lowest sync-ing priority, so even if you tell iTunes to
sync your whole photo library, it will only sync as many photos as it can (if any) into the space it has left on the
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TV after it has sync-ed all your other selected content (movies, tv shows, music, podcasts). You don't have to worry about photos taking up any valuable
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TV HD space that you need for other content.
Because of the way Apple set this up, though, you will still be able to
stream any selected photos that couldn't fit onto the
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TV's HD.
So, why not allow streaming of your entire photo library regardless of what you chose to sync? Well, in my case our
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TV is used by several people, and I don't want everyone that uses the
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TV to have access to my entire photo library. By only streaming the photos that are selected to sync, I can control which photos in my library are 'publicly' accessible via the
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TV, and which are private.
Why stream your 'public' photos if you've already selected to sync them too? In my case iTunes will never sync any photos, because I have too much higher-priority stuff set to sync already, so if I'm going to view any of the photos from my sync-ed computer I'll only be able to do it by streaming. Said another way, all of the selected photos will be available by streaming, even if only some (or none, as it is for me) are on the
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TV's HD.
If you want the whole photo library from your sync-ed computer available by streaming, just tell iTunes to sync all your photos. It won't be able to sync them all, but they will all be available by streaming, and they won't take up any
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TV HD space that you need for anything else.