Managing RAW image Files on several machines

Question

I am a new user of Lightroom, purchased three weeks ago, and trying to switch from Aperture, which doesn't support my newest addition to my equipment, the Canon G9 RAW files. I feel resonably comfortable after these weeks with LR's basic concept's, with the exception of how it manages files. I just don't get it after going through the FAQ and the online help resources, and trying to slug it out with Martin Evening's book on LR from Adobe.
I have several hundred Gb of RAW images from a variety of sources. I need to be able to read and manage LR from two different machines, my MacBook Pro and my Mac Pro. I also need to be able to manipulate the images in various folders. My images are now contained in folders on an external drive(s). I need to keep the RAW original images for future access, keep the LR image information so it can be read by different machines, and be confident of neither losing the original RAW files nor losing the metadata and LR image edits. I want to keep all of the image information on external drives that can be accessed by physically connecting them to one of the two machines.
I think my problem is in not understanding the concepts in LR of a "library", a "catalog" and a "collection", nor understanding how to manage the images using these concepts.
Any help would be deeply appreciated.

Answer 1

William,
Lightroom cannot modify the image portion of a RAW file, although sometimes the image metadata can get modified. Here is a thread where Chris Birchall and I explain that in detail:
http://www.adobeforums.com/webx/.3c0331a6/13
Regarding workflow, Larry brings up a good point. Lightroom overall is a fantastic ver.1 product, it truly is. The printing functionality needs beefing up and this multi-user multi-copy situation can be troublesome.
If you use only one external hard drive then the method I described above might work fine. Things I'd do if I was running such a setup:
--Use 2 folders, one named Lightroom and one named Photos, on each machine and on the external drive. Store the Lightroom catalog, folders, etc. under the Lightroom folder. Make all subdirectories/subfolders under the main Photos folder as needed for your photos.
--Do not import your photos into LR's database, import them in place and leave them as-is on the disk. A metadata-only catalog file size will be much smaller than a database containing 1000s of photos and will copy much faster.
--Back up your Lightroom directory after every working session.
--Back up your Photos directory any time you add new photos or rearrange the directories/subfolders so all 3 directory structures and contents (laptop, desktop, external drive) are always identical. Since your main LR catalog is on your external disk, your backup can be the copy on your laptop or desktop.
--Keep the copies straight in your mind (harder than it sounds).
--Try to name your on-disk folders as close to your Collections names as practical. A bit more work but makes things easier to find and makes deleting photos easier. You cannot delete while in a Collection, hopefully they'll fix that.... Anyway, when your Collection and Folders names are way out of sync it can be a hassle to track down where that Collection photo is on-disk if you want to delete it.....
One area that might get out of sync is when you want to delete photos from your disk. It's easy to add new photos to your backup machines but not easy to delete them everywhere.... In that case you might sometimes want to delete a folder/subfolder and re-copy the whole thing.
Cheers,
Robert