Here's the tale. My camera was excellent for the past year or so, and served me well no matter what ROM was being used. One fateful day, I was going to share something to a friend on Google+ while using the Google Play Edition ROM (really very excellent) when I was presented with this message:
I didn't think much of it, but let it sit while it did this. I eventually came back to the phone after several minutes, only to find the message still there.
I killed Google+ and opened my camera. I was presented the same message that the camera firmware was updating and to wait. I let it sit for about half an hour. I tried again only to receive the same message. Eventually I was presented a black screen with the camera controls, and was able to switch to the front camera. However, the back camera was still only a black screen. I restarted and had the same issue.
I reflashed to a stock based ROM (Insane) and was presented with the same issue, only this time no warning about firmware upgrades in progress - just black screen on the rear camera. At this point I decided an ODIN would probably take me back to where I needed to be, so I ODIN'ed a stock image. The issue was still persistent, but the camera would work every once in awhile now. It was a very rare occasion, but sometimes the back camera would flicker into life and allow me to take pictures as usual. Infuriatingly enough, the first time it started working was when I was trying to show a friend of mine, also into Android, the issue.
Non-TW based ROMs do not work with the rear camera now. The front camera is still working, and sometimes allows videos to be taken.
TW based ROMs rarely work with the rear camera now. The front camera is still working, and sometimes allows videos to be taken.
Does anyone have any ideas on remedies for this issue? Is there a stock Samsung Galaxy S4 camera firmware flashable? I've searched around, and decided to yield to the higher XDA powers of knowledge after no returns.