iCloud Photos lets you keep full-resolution versions of your images and videos in iCloud storage, while letting you choose to store just optimized versions—thumbnails and low-res video previews—on your iPhone, iPad, or Mac. That’s great, especially when you have more media than storage. When you need the full image or video, you can double-click it within Photos to retrieve it for local use.
The conundrum can come when you want to load a massive amount of media data into Photos on a Mac set to Optimize Mac Storage (in Photos > Preferences > iCloud) all at once instead of adding to it over time. The trick is to stagger your import. Let’s say you have—as one Macworld reader did—600GB of media data and a 128GB disk drive in your Mac.