Transfer Photos from Photos App

Photos that are not in the Camera Roll are photos that were synced to the iPhone from the computer via iTunes. Those photos would be in the backup of your old computer. After they are synced to the iPhone, they are reduced in size and resolution. The only way to get them is to purchase some 3rd party software to get them out of the iPhone backup.

If you do not have the original photos on your computer you need a third party app to help with the transfer.

I often use Photo Manager Pro. You can copy photos from your Photos app into Photo Manager pro. I then use an ftp application on my computer to wireless copy photos from my iPad to my computer.