Exclamation mark on images in iPhoto

Problem

In iPhoto, one (or several) images show an exclamation mark when you try to open them.

Cause

iPhoto is unable to find the location of the image.

Solution

You can try the following for each photo with the problem:

1. Click on the photo.
2. Click the Edit button located in the bottom right.
3. Click the “Revert to Original” button.