Hey, guys. I use Lightroom and was introduced to XMP. I love it, since I can transfer my .NEF into another hard drive and be able to get it back with changes to the .NEF intact. My aunt plans to use Aperture 3 and we're wondering if it's possible to do something like that. Basically, it's: 1) Import .NEF from memory card to laptop 2) Work on .NEF then export as .JPEG 3) Keep .JPEG on laptop and back it up to another hard drive 4) Move .NEF to another hard drive 5) Retrieve .NEF in case I need it again and still have the changes like Lightroom's XMP. Thanks. edit: oh yea, in case anyone knows. how much photos till lightroom lags? i hear 20,000? i'm not sure if i should start using different catalogs organized by years (2008-2009???).