Why is my Mac HD filling up when I import to an external library??

[Shacklebolt]

Using a MacBook 2.4ghz/2GB/150GB, and an external 500GB. This only happens intermittantly, but I have no idea what's causing it:

Using image capture to pull NEFs from my D300 directly onto my external. Have an external iPhoto library on that HD, which I am 100% positive I am running iPhoto off of. Image capture library on external HD. Library on external HD.

When I import photo files on the external to the photo library on the external, my Mac HD **sometimes** temporarily gives up the same amount of space as if I were importing the photos directly onto it. So I import 1GB of photos, capacity of external goes down by 1GB (which is fine), but capacity of my Macintosh HD _also_ goes down by 1GB? Then I have to reset the computer for the missing 1GB to reappear?

What the heck is going on?

 

[Ruahrc]

My only guess is that the process of importing is using up virtual memory on your iMac HD- which will show up as data written to your internal drive until the next reboot, when the virtual memory cache gets cleared out. This should not be a big issue as I think there is some upper limit on virtual memory usage after which the OS will start overwriting the oldest data with newer data.

Ruahrc

 

[And1ss]

maybe, the image previews/cache is what is taking up some of the space.