I want to save certain Photos stored on my Mobile devices to the Cloud. However my Mac Desktop Images backs up to various External Drives, as these 100,000+ photos/videos would exceed my iCloud limit. Can I therefore just sync my portable devices and not my Desktop computer?
iPad, iPadOS 13
Yes you can. Check this:
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How do I turn off iCloud Photos on only one device?
You can turn off iCloud Photos on a single device when you follow these steps:
If you have Optimize Storage turned on, you might not have all of your original photos and videos on your device. To download the original photos and videos on your iOS device, go to Settings > [your name] > iCloud > Photos and select Download and Keep Originals. On your Mac, open Photos, choose Photos > Preferences, then select Download Originals to this Mac. Then you can turn off iCloud Photos. You can also select the photos and videos that you want to download from iCloud.com.
Before you turn off iCloud Photos, you might want to make a copy of your photos and videos.
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copied from: Get help with iCloud Photos - Apple Support
Yes you can. Check this:
...
How do I turn off iCloud Photos on only one device?
You can turn off iCloud Photos on a single device when you follow these steps:
If you have Optimize Storage turned on, you might not have all of your original photos and videos on your device. To download the original photos and videos on your iOS device, go to Settings > [your name] > iCloud > Photos and select Download and Keep Originals. On your Mac, open Photos, choose Photos > Preferences, then select Download Originals to this Mac. Then you can turn off iCloud Photos. You can also select the photos and videos that you want to download from iCloud.com.
Before you turn off iCloud Photos, you might want to make a copy of your photos and videos.
...
copied from: Get help with iCloud Photos - Apple Support
You can choose to enable iCloud Photos on your portable devices and not on the Mac.
Saving photos from iPad and iPhone to iCloud.
