Photos is a built-in iPhone application that organises and displays photos that you've take on your iPhone and that you have imported from iTunes. The application allows you to delete individual photos from the photo albums directly from your iPhone. However, if you want to delete an entire photo album, you have to use iTunes to remove the album as part of the sync process.
Attach the iPhone data cable to the bottom of your iPhone and connect the other end of the data cable to an available USB port on your computer.
Open the iTunes application on your computer.
Select your iPhone from the list of "Devices" on the left side of the iTunes window.
Click the "Photos" tab.
Select the option "Sync Photos From selected folders". Un-check all photo albums that you want to delete from your iPhone. Click the "Apply" button.
Wait for your iPhone to sync with iTunes. When the sync process is complete, iTunes will prompt you that it is safe to remove your iPhone from the iPhone data cable.
You can delete individual photos directly from the iPhone's Photos application. Select the picture you want to delete and then tap the rubbish bin icon.