I want to help a friend get setup with iCloud Photo Library. They have an iOS device without a lot of free space and they have a PC and an old Mac that can't run Photos.app. In addition to using iCloud Photo Library they want to back up their original photos from their iPhone to their PC or old Mac. I don't think this would be an issue except they don't have enough space to store all of their originals on their iOS device so they must use the 'Optimize iPhone Storage' setting. My fear is that they will only be backing up thumbnails when they go to backup their photos to their desktop. Is there anyway around this?
They may have updated the iCloud Photo Library for Windows capabilities:
What you can do with iCloud for Windows
Safely store your photos and videos in iCloud. With iCloud Photo Library, any new photos and videos that you take on your iPhone, iPad, or iPod touch automatically download to your PC. And you can upload new photos and videos from your PC so that you can access them from your other devices too.