Dropbox allows you to backup photos & videos, edit or apply filters to a photo, share them with family and friends, and much more. If you apply edit or filter to a photo on your iPhone or iPad, then it will store in the metadata included with the photo. So the raw photo which includes the metadata, is then uploaded to the Dropbox servers. If you view the photo using an app or software that can't interpret the new metadata, then You will see the original photo without modifications. When uploading a photo, the Dropbox app is given a thumbnail of your photo with the modification applied. You can see the edited thumbnail of your photo during the automatic Camera Upload process. You can also see the edited thumbnail of you photo in your 'Photos' tab for manual uploads.