If you have a large photo album, you can quickly see iPhoto start to take up large amounts of hard drive space. One reason for this is that every time you modify a photo (rotate, enhance, etc.) it creates a backup original. This is to allow it to have that magical "Revert to original" option.

If you have decided that you don't want your originals any more, getting rid of them can reduce the amount of hard drive space that your photo library takes up. There are two ways of doing this - using a few terminal commands, or using a free application called iPhoto Diet.

The terminal commands are from this MacRumors forum and come with a brief explanation of what they do. To run them, paste the following into the terminal:

mkdir ~/.Trash/iPhoto-Originals
cd ~/"Pictures/iPhoto Library/Modified/"
find . -type f -exec mv "../Originals/{}" ~/.Trash/iPhoto-Originals/ \;

This gives you a folder in the trash so you can check all the right photos are there before emptying it permanently. A summary of everything in the MacRumors forum has been made by Adriaan Tijsseling on his blog.

iPhoto Diet is a free application by Martin Fuhrer that does the same thing, but with more options and a nice user interface. This may take a little more time than the terminal commands, but it is much more user friendly and gives greater flexibility. It allows you to reduce you photo library size in the following ways:

• eliminate duplicate photos created internally by iPhoto or imported by yourself
• remove iPhoto's backups of rotated or modified photos
• strip the thumbnail icons of your photos
• remove thumbnail photos that have become mixed up with your high resolution photos
• identify photos which have not been added to albums
• weed out unnecessary folders and files from the library
• and more!

Download Links, installation instructions and an FAQ are available from Martin Fuhrer's site.