>>FIRST, is your external media: CDs, USBs, existing external drives etc. Here, you will open up those files and copy their entire contents to your external hard drive (Disk A). At this point do not worry that it all seems a bit of a mess (we will get to that). And don’t worry if you want to keep the photos or not – just grab everything. When you have completed steps 1 through to 8, you are ready to toss out all those bits of paraphernalia that you will never need again, eg CDs.
>>The SECOND part of the process is to get your “internal” media, out of your computer and onto your external hard drive. You will need to know where photos are stored. There might be photos on your desktop, photos in your documents folder, photos in the download folder, but most of your photos will be stored in your photos application. So we need to get most of them from there. Not too hard on a PC because photos are stored as individual files and can be simply copied across. For Macs it’s a bit more complicated. Why?? Because Apple is driving you to use (paid) iCloud as the solution. Mac computers use ‘Photos’. You will need to “select all” and then “file export”, “original photos”, using “sub folder format”, “moment name”. And export them all to your external drive. Check they are all there.
>>The THIRD part of the getting-photos-from-everywhere process, may, or may not relate to you, but it involves downloading any iCloud photos onto your computer. [If you don’t use a cloud service, SKIP this step as described below].
If using a MAC, while in ‘Photos’, go to ‘preferences’, ‘iCloud’. Check, “iCloud photos” and “download originals to this Mac”. Now, BEFORE you do this, you may need to DELETE the photos that are currently there in ‘Photos’, because you may not have room for them on your computer. But ONLY do this, if the 15492 photos that are in ‘Photos’ are all showing up as having all been copied to your external drive (in their original quality). After deleting, what you have exported to your external drive, then delete your deleted items. Now download from iCloud. This process can literally take hours, possibly longer. When they are all downloaded in all their original quality glory, copy these across to your external drive. Put them in their own folder called iCloud photos. AFTER THIS, you “may” want to delete all pictures in iCloud. For example, if you don’t want to pay apple storage costs any more. But don’t do this if you want to access iCloud photos on your phone.
By the end of Step Two, you should have all your photos on the external drive, but they are still a mess, and you’ve probably got many duplicates, which brings us to…