If you have a Windows Phone, the capability of having your new photos immediately replicate to the Skydrive Camera Roll and then to all your SkyDrive devices is a super-useful feature. However, I was often unclear exactly what the replication rules are between the phone and SkyDrive because deletions didn't always work the way I thought they might. So, I ran some tests this afternoon.
The bottom line
Replication from your phone’s Camera Roll to SkyDrive is a one-way deal. Once your photo replicates out to Skydrive, any changes you make to the photo on your phone and any change you make to the SkyDrive copy are entirely separate.
If you delete a photo from your Camera Roll on your phone, it’ll still be on Skydrive (which is often a good thing).
If you delete a photo from any of your SkyDrive-connected devices or the SkyDrive web app, the deletion operation will replicate to all other devices – but it’ll remain untouched on your phone. (It will remain in the Recycle Bin on your devices and in SkyDrive.) Windows 8.1 Skydrive files are, by default, "smart files" that contain only the metadata about the photo, but the replication process works the same as if they were the entire file.
So if you really want to get rid of that New Year's selfie of you with the lampshade on your head, you’ll have to delete it from both places.
And in case you were wondering, if you choose to save an image from another album on your phone (for example, Saved Pictures) to SkyDrive, it will upload to Mobile Uploads.