iPhone shows photo usage but iTunes correctly shows no photos
I have an iPhone 4s running IOS 6. After deleting all photos from my phone by emptying the Camera Roll and unsyncing photos via iTunes, I see a discrepancy. The phone's Photos app is empty, as expected. iTunes shows no data allocated to photos, as expected. But when I look at the phone's Usage (Settings>General>Usage) there is 4.8MB in Photos & Camera that won't go away.
At first I thought it was because I had sent some photos via iMessage, so I deleted the iMessage conversations. No change. Have reset the iPhone numerous times; have deleted content and settings and restored from both iCloud and iTunes backups. The phantom photo usage won't disappear.
Anybody have any ideas? I'm not running out of space -- I just don't like not understanding what's being reported.
iPhone 4S, iOS 6