To transfer photos from your iPhone onto a PC, it is prudent to use a tool like ImTOO iPhone Photo Transfer to keep the original file quality.
ImTOO iPhone Photo Transfer allows you to transfer images or digital photos from your iPhone onto your PC. It offers you a preview window where you can view your photo in normal size or in thumbnail mode before the transfer. ImTOO iPhone Photo Transfer can adjust the orientation of your photo automatically and allows you to connect several iPhone simultaneously. In addition, it can also be used to manage, to organize and to edit the photo albums on your iPhone.