
So if you have any doubt about whether the photos in Photos can be discarded, extract them all using humboldt32's advice, import them into Picasa, and then delete duplicates.
IPHOTO LIBRARY MANAGER PHOTOS FOR MAC
If you are not sure if you have duplicates or not, it looks from googling that Picasa for Mac maybe does not have "duplicate detection" built in, but there are some free tools you can download thaa will help you find/delete duplicates. (Although I would recommend moving it to a flash drive or external hard drive for safekeeping, just in case you decide you need to restore them). If you are 100% sure you already have copies of the photos that show up when you launch Photos, then you can delete the. If you need to rescue your photos from Photos.app, humboldt32 has your instructions. So at some point, you intentionally imported some of your photos into iPhoto? What was your photo storage strategy at the time? What I am getting at is: are all of the photos you see within the iPhoto/Photos app duplicates that can be discarded, or do you think you need to extract those photos from the Mac photo app(s) and get them into Picasa where you want them? It does not index or reference images ( technically, Photos can reference photos outside its Library, but it is not likely you are doing that) The way Photos (and iPhoto before it) works is that it imports all of the images you feed it into a special file format that intentionally hides the underlying folder structure from you (as tomierna explains above).
