"The Mystery Annoyance of the 'Your iPhone Storage Is Almost Full' Message" has been solved. You're Welcome.
I take a lot of photographs. A LOT. It's a sickness that has exacerbated since the advent of digital photography, and the purchase of my first digital camera, an Ixla, back in 1999. Oh, and now that I have been able to take photos with my cellphone for well over ten years now, I take photos of damn near everything. I take photos of clouds. I take photos of trees. I take photos of random stuff like fruit in the supermarket, or buildings in Manhattan. I take photos of things going on around me. I take photos.
My first iPhone was a 3s, and then I went to the 5, and then the huge brick of a 6+. I'm still trying to get used to holding it and taking photos with the volume button without putting the phone in sleep mode by mistake because the designers at Apple moved the sleep button from the top to the side. Awkward! Anyway, for several years now, I have had to upload all of my photos to the iPhoto/Photos library and delete the photos on the phone to free up storage space. I would back the photos up though my old MacBookPro to an external hard drive. I got used to that for a while.
Then Apple introduced iCloud photo storage. I thought it was the greatest idea since peanut butter! I could upload all of the photos I could find to the cloud, and then have them made instantly available on my iPhone! This was awesome! I had upwards of 132,000 photos on this on particular external hard-drive alone, and I you're telling me that I could see them on my phone whenever I wanted so I could share them from anywhere? This was tremendous to me. I instantly became an uploading freak!
Since I am constantly (and annoyingly at times) taking photos, instead of storing all of the full sized photos in my iPhone's memory, I chose the option to upload full resolution photos to the cloud and keep tiny optimized-for-performance thumbnail versions on my iPhone for reference. Now my iPhone was chock full o' these thumbnails, and when I opened one, it would pull the original in from the cloud. Did I mention I had 132,000 photos?
I began getting messages that my 64gb of storage was full. How could this possibly be? I did not have this phone *that* long. I checked my iPhone's storage, and I was being told that I had 37gb of photos in my phone. (Yes, in a row!). For the life of me, I could not figure out how to delete the thumbnails from the phone to tell the cloud I just didn't want them on my phone, but I always got a message warning me that deleting the photo would also delete it from all of my libraries. NOooo!!! Than's not what I want at all!!
I googled everything I could think of to figure out how I could delete the photos from my phone once they have been uploaded. I had read time and time again that you *can't* delete them; you can only optimize your storage. It seems that they are implying that you need to have WAY more storage space on your phone to handle the thumbnails if you have so many photos in the cloud; In other words, you *can't* delete them from your phone without deleting them everywhere.
Or so I thought.
I found a page on the Apple forum where someone had a very similar question, and I read the entire thread. A definite answer to my specific dilemma was not given; however, it was firmly established that as long as you have your phone set to iCloud storage, those photos will NEVER GO AWAY, and if you turn the storage OFF, they will not go away, either.
But therein lies the answer. If I TURN OFF communication with iCloud photos, the thumbnails are exactly that, and can be deleted without their being removed from the cloud. If you want them back, you can always turn the cloud back on again.
But already I digress. I do not wish to turn the iCloud back on for my iPhone photos. I also recently became the proud renter of the Adobe Creative Cloud suite, and they offer unlimited photo storage in the cloud. I can also preview all of these photos in Adobe Lightroom, which would now make using the iCloud photos through my phone obsolete in a way. It does not seem to jam up my iPhone with data.
I was afraid that I would not be able to use some of my favorite photo apps, such as TangledFX, Over, and Tiny Planets without first downloading the photo to my camera roll, but Lightroom allows me to open the photo in just about every photo editing app I own (except for my favorite, Enlight. Get with the program, Enlight!).
So, how did I delete the thumbnails? After I turned off the cloud on my iPhone and tested a few deletions without losing them in Photos or iCloud.com photos, I went into my photos, backed out to the 'Years' page, went forward to 'Collections', chose 'Select', and then selected every moment. When I was done with this, I hit the trash can. Are you sure you want to delete 7,000 photos? YES, I am.
Now that I had done that, I needed to go into my albums, and look for the 'Recently Deleted' album; iPhoto will keep your deleted photos for 30 days unless you tell it otherwise. With that, you can 'Select All' and permanently delete them.
Shazam. I freed up 37gb of storage space, my photo library takes only 6.7gb and Lightroom uses less than 1gb.
I then ran another test. I first turned my photo sharing back on. It did not change my storage usage.
This time I turned on the photo stream Surely this would add thumbnails to my storage. Nnnnnnope!
So, there you have it! "The Mystery Annoyance of the 'Your iPhone Storage Is Almost Full' Message" has been solved. All of my photos are now backed up into both Apple iCloud and the Adobe cloud, and when I'm confident that I have everything in the Adobe cloud, I will download my entire iCloud library onto a separate external hard-drive and ditch the monthly charge with Apple.
I also have a slew of new creative iPhone apps I can use within the Adobe Creative Suite that I actually have room for on my phone now, such as Photoshop Express, Adobe Voice, Adobe Premiere Clip, Photoshop Fix, Adobe Illustrator, Capture, Mix, Slate, Portfolio, etc. I can't wait to start using it all, now that it's all in some kind of order now.
Did you know that if you have Amazon Prime, that you have unlimited photo storage there as well? There's no such thing as too much redundancy when it comes to photo storage.