So the Photo's app is starting to churn though my 160Gb photo library - (which will be fun on my 1mbs connection) Anyway I have a quick question please as the App isn't clear. Under "Preferences" - the "iCloud" tab on the first page. You have a choice to select one of two settings. 1) Download Original to this Mac or 2) Optimize Mac Storage I'm a bit confused - I don't want to loose any of my original resolution photos. If I choose the first option "Download Original to this Mac" - then I assume the version that is kept in the iCloud library is a compressed version of the original - and the original big-resolution photo is kept on my Mac. If I choose the second option - Optimize Mac Storage - it says it keeps an original high resolution version of the photo in the iCloud library - and also an original version will be kept on your mac - assuming there is sufficient room. Now I do have plenty of room on my Mac - but the real attraction for me is to use the iCloud backup as a way of keeping my library safe in case of hard drive failure - or even theft..... So for me - should I choose the second option - and assume this will take a lot longer to upload as its effectively copying my entire photo library in its full resolution to the iCloud photos account?...and so my iCloud drive will suddenly have another 160GB in it?? And if I use this second option does that mean - every time I take photos on my camera and put them on my Mac - they will automatically be also uploaded to iCloud in their full resolution - and will also stay on my Mac in full resolution?? Thanks for any thoughts or advice.