Once your Aperture library crosses the 10,000 image mark, you will likely pause to wonder if you’re going to run out of space any time soon. You may have already looked at the size of the Aperture Library file in the Pictures folder, and thought “whoah… 150GB… so that’s why I’m outta space”. But wait, you’re working referenced; all those massive RAW files are on an external drive, how is this even possible?!
Previews. Aperture 1.5 introduced a series of amazing features that allowed you to carry around an enormous number of photos on a single computer, while at the same time leaving your RAW files on other drives, and still letting you share those photos throughout the OS. They way it handles this magic is through JPEG Previews and XML.
Understanding how this works will allow you to control the size of your library and relcaim 10’s – or even 100’s! – of GB’s back.