If the Camera app and Photos app on your iPhone disagree about the contents of your camera roll, you may find yourself needing to get "under the hood" of your iPhone to fix the issue. Fortunately, you can do this without having to jailbreak and hopefully without losing any pictures.
The Camera app saw pictures in his Camera Roll, but the Photos app claimed the Camera Roll was empty. This was preventing iPhoto from synchronizing his pictures.
The first problem was figuring out how to get all the pictures off his iPhone. The second problem was figuring out how to getting the Camera and Photos apps to agree about the contents of his camera roll.
A few years ago, when I had a similar problem with my iPhone camera, I was able to solve the problem using Ecamm's $20 Mac utility PhoneView.
I've written about PhoneView before, and two years ago Dave Caolo even wrote about fixing a bug in iPhone's camera roll, but obviously this is still an issue.
PhoneView gives you access to the data on your phone, regardless of whether it is jailbroken or 'vanilla.' Obviously there are some limitations to what it can access, but for things like pictures and music it can be invaluable.
The first step is to enable the "Show Entire Disk (Advanced Disk Mode)" preference in PhoneView. Turning on that feature will pop up a disclaimer that if you aren't careful you can cause data loss. Let's proceed with caution, but without undue fear.
Once you have Advanced Disk Mode enabled, click on the "Disk" folder under "Data" and look for the two folders highlighted here: DCIM and PhotoData.
Select both of those folders (as shown here), and then click "Copy From iPhone" from the toolbar. This makes sure that you have a local copy of the information, including your pictures and videos. You must confirm that you have all your pictures and videos before continuing.
Aside: there may be another folder called "Photos" which I believe contains the pictures which are synchronized to your iPhone from your Mac via iPhoto or Aperture. Leave that alone.
Once you are sure that you have copied all of your pictures and videos from your iPhone to your Mac, click the "Delete" button.
Now, unlock your iPhone and take a new picture, and you should find that the iPhone has re-created the necessary folders and started a new fresh Camera Roll. Problem solved.
PhoneView costs $19.95, however a free demo is available. Check out the website for a fuller description of all the various features that PhoneView offers. It's definitely worth the cost if you want to backup lots of various pieces of information such as SMSes, phone call lists, even voicemails.