Hi chappello,
Welcome to the Apple (user-to-user) Community.
Re: it seems that my computer thinks the photos are saved on the Mac even though they definitely are not ..... any solutions?
Am no expert on storage, yet your question surely deserves a reply. Even if only to get a discussion started, so others with expertise may see fit to join in.
Would be great to know which MacBook Air model (year) we are discussing:
How to: Identify your MacBook Air model
Please excuse if anything below is already well-known to you.
Wondering if you "restart" your Mac occasionally, as that can often help clear out temporary files etc., and check that the trash gets emptied, as trash takes space.
(If you delete trash / files, the storage estimate may not change until you restart. (ie: Apple menu > Restart ... wait ... log back in)
First step when free storage space is lacking is generally to back-up everything.
Best place for an accurate estimate of storage: Apple Menu > About this Mac.
Re "other" (or system) storage:
Although we can not safely delete anything in there, there can be files that belong to apps, yet are included in the storage estimate ... so checking carefully through apps for any large files can sometimes assist in reducing the amount.
Am not sure how that is easily done in MacOS 10.12 Sierra:
(FWIW: Here's how in the most recent MacOS: Find and delete files on your Mac – Apple Support (may give some idea ?)
or
Maybe looking for "Optimise storage space on your Mac" in your Mac's help ?
All the best :-)
