How to transfer photos from internal storage to SD without impacting Google Photos and Dropbox? I normally use my SD card to store photos. Due to some changes, photos I was taking were stored in phone storage for some time. I am back to storing them on the SD card. I am therefore left with ~500 MB of photos on phone storage instead of the SD card.

When taking a photo, it is automatically uploaded to Google Photos and Dropbox. In both cases (when the photos were going to the phone storage as well as now, when they land on the SD) they were correctly uploaded to both of these services.

I would like to understand how I can move the images in the internal storage to the SD without impacting the online storage (that is: without modifying it). In particular I would like to avoir re-uploading them, duplicates and changes in the timestamp.

Are the online services resilient on changes happening on the phone? In particular:


is the uploading process making sure that the photo which has changed (in my case: location on the phone) 
would a full re-upload of the photos modify the online content (it could be that the photos are uploaded but Google Photos and Dropbox realize that the file already exists and just discard it). I do not care about the upload bandwidth, what I am worried about is the possibility of duplicates or (if the images are overwritten), of a change in the timestamp.


Is the impact of such changes on the phone documented somewhere?
Note: this answer is based of experimentation and some speculations at the end.

I tested with a few pictures, and then with a batch move of the pictures from phone storage to the SD card.

The result was OK: the pictures online did not change, there was no upload despite pictures appearing on the SD card.

I assume therefore that the phone does some housekeeping and keeps a trace of what was uploaded (so that it is not uploaded again)