Delete all photos from iPhone 4S

When ordering my new iPhone 4S about 2 years ago, I thought 16 GB would surely be enough - boy, what a mistake.

Since my photo collection (> 2600 photos and a couple dozen videos) was about 9.5 GB in size, I decided to remove all of them and re-import only the most important ones. Sadly, the photo app doesn't have a "Remove all" button, but as usual, the Internet provided a quick solution:

• connect iPhone to Mac
• open Preview
• File -> Import from iPhone
• Select all (Cmd+A)
• click the "Delete" button in the lower left corner

(see https://discussions.apple.com/thread/3777283?start=0&tstart=0 for alternative approaches)