I've spent the past couple days messing around with iCloud photo library and discovered an oddity this morning.
When I configured iCloud photo library on my phone, I set it up with the "download and keep originals" option. I assumed that when my photos were uploaded to iCloud, they would be uploaded at their full resolution, which would then allow me to pull photos from the iCloud.com website (Since there is no OSX app for photos)...... I assumed wrong...
I tested this by taking a photo with my phone (5 minutes ago) and ensuring it was uploaded to both iCloud and OneDrive. I then went on the iCloud and OneDrive websites and downloaded the photo to my computer.
I was shocked to see that the photo in iCloud downloaded at 820kb with a resolution of 2048x1536. The EXACT SAME photo downloaded from my OneDrive account comes in at 1,796KB and a resolution of 3264x2448
Morale of the story?? It appears that iCloud is NOT storing full resolution photos (unless I am totally doing something wrong). Go ahead and test for yourself!
I have noticed this as well. I turned on iCloud Photo Library yesterday and it finally finished uploading my photos and videos today (I have about 500 on the phone). Now I am able to login to iCloud.com and see my photos, but like you said, when I click the download icon, it downloads a smaller version, not the full-resolution photo. And I too have enabled the toggle to keep full resolution photos on the phone, but that shouldn't matter because full resolution photos are supposed to be uploaded to iCloud.com either way! The toggle is just there to save space on your phone.
I don't know what exactly is going on, but it could be one of the following:
1) Maybe by setting the toggle to keep full resolution photos on the phone, it only uploads optimized versions on iCloud.com? This doesn't make sense, however, as iCloud Photo Library is advertised as automatically uploading full resolution photos and videos and uses your storage space. The toggle is just there to keep optimized photos on your PHONE so that it saves you space on your device. NOT LIKELY.
2) Maybe iCloud.com is just showing you and allowing you to download a smaller version? Since iCloud.com photos just appeared and is in beta form, it just doesn't yet have the capability to download at full resolution? This doesn't make a whole lot of sense either since the version that is downloaded from iCloud.com isn't THAT much smaller than full resolution. And if it IS just optimizing when downloading, then how can we confirm whether the full resolution photo is actually on iCloud.com or not?
TEST: Try logging into iCloud Photo Library from another iOS and sync the full resolution photos to that device from iCloud. Then have that device auto upload to Dropbox or Google and see what the resolution is. If it's full resolution, then we'll know that iCloud is storing the full res version but somehow iCloud.com is just not downloading them. If the newly synced photo is lower resolution too, then we'll know that iCloud is downsizing them before re-syncing with another device. I haven't tried this myself, but it would be a good test! (hint, hint)
3) Perhaps the toggle on the iOS device is broken and the photo is optimizing the photos before uploading them to iCloud? This doesn't seem too likely either since it would be a pretty big blunder and is fundamentally opposed to how it's supposed to work. I wonder what would happen if you set the toggle to optimize on the phone and then take some new photos?
One thing is for certain: iCloud Photo Library is definitely in BETA form and should not be relied upon as a sole means of backup or syncing. I continually watched my upload and it would often get stuck or start over (it seemed). Sometimes it would say it's down to a certain number and then it would jump back up again. It finally did get them all backed up, but it wasn't straight-forward at all. I'm wondering if it backs up a smaller version first, and then starts again and uploads a higher resolution version? Again, that doesn't make much sense since it would be unnecessarily using iCloud storage space.
I'll continue to use Google+ backup for now as that works great (though I have to open the app frequently to get it to do the backups). But at least it uploads at full resolution and there's a lot more I can do on Google+ on the web than I can iCloud.com Photos. But then again, Apple is just getting started, so they have a lot of work ahead of them.
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I sorta agree - I'm assuming web is only rendering reduced sizes to minimize a huge download of a page(s) - and the when iCloud Photo goes to 'production' they may have like 3 buttons that has different download size options?
Or maybe that's the only size they'll ever be able to be downloaded at from iCloud.com. Remember, early next year we'll get the Photos app and the full resolution photos will likely automatically download and sync to the computer at that time. Maybe the limitation on iCloud.com is on purpose since it is web-based? At any rate, it makes iCloud Photo Library both risky and limited at this time, so I wouldn't recommend it to anyone who isn't willing to be a tester.