Apple already has a support doc explaining how to do this. They got it basically correct: you copy the files to a folder, then burn the files from that folder. The problem: you’re copying a bunch of files from one place to another one the same drive, which takes a long time and uses up disk space – which you may not even have free. I just needed to burn 1,080 photos to a DVD, total size about 3GB.

Thankfully, there’s a good solution for power users:

  1. In iPhoto:
    1. Select the photos you want to burn. (I recommend using an album, but that’s your call.)
    2. Choose Share->Desktop
  2. Close the System Preferences app when it pops up
  3. In Finder:
    1. Right-click in a folder or the desktop, and choose “New Burn Folder”.
    2. Open a Finder window and navigate to:
    /Users/username/Pictures/iPhoto Library/iPhoto Selection
    1. Select all the items in the folder, and drag them onto the Burn Folder.
    2. Open your Burn Folder and start the burn normally.

There! You’ve burned your photos to a disk the way it should always work, using aliases – no needlessly duplicating files on your hard disk!