Connect iPhone to your computer. In iTunes, select iPhone in the sidebar, then click the Summary tab. Deselect Automatically sync when this iPhone is connected. You can always sync by clicking the Sync button.
Prevent automatic syncing for all iPhones and iPods:
In iTunes choose iTunes > Preferences (on a Mac) or Edit > Preferences (on a PC), click Devices, and select Disable automatic syncing for all iPhones and iPods.
If this checkbox is selected, iPhone wont sync automatically, even if Automatically sync when this iPhone is connected is selected in the Summary pane.
BTW; On a Mac, photo's don't sync onto computer automatically, (unless using iCloud or something). They will back up onto your Mac if that is checked though.
I assume you are talking about a PC computer, right? Hope it helped you.