Aperture is structured to provide exactly what you want. You have a few details mis-understood, however.
Read my short guide to the parts of Aperture.
Your Library holds Images (each Image is a record in a database). You control whether the Image's Original (the file you imported) is stored inside the Library package or outside. Images that are stored outside the Library package can be on-line or off-line (Images stored inside the Library package are on-line any time the Library is open in Aperture.) Aperture lets you do much with Images whose Originals are off-line, all of which involves metadata: you can rate them, put them into different containers in Aperture, assign keywords, etc. What you cannot do when an Image's Original is off-line is: print the Image, change Adjustments, or export the Image.
Aperture is designed to deal with the problem of Libraries taking up too much space an a single drive by relocating older or rarely-used Images' Originals to a second (almost always external) drive.
Cleverly, though, Aperture also includes another file based on your Image that can be useful. This is the Preview. It is a JPG file. It is stored in your Library package, and thus is always on-line when your Library is open. You create a copy of your Preview file by dragging an Image from Aperture. Those copies can be emailed, used in other programs, etc. (Added: In fact, it is this Preview file that Aperture makes available to other programs via OS X's Media Browser.)
You control:
- whether Previews are created
- whether Previews are deleted
- the size and quality settings of the Preview file.
You can control these things for each Image in your Library, but in practice this is usually set for the entire Library and not changed for any subset of Images.
Put your Library on your system drive. Relocate [some, many, almost all] Originals to a dedicated external drive. (Note that this is not a one-way trip: Aperture makes it easy to relocate or consolidate any Originals at any time. And don't worry about the Finder folder structure: it seems important to you, but to the computer it makes no difference at all.) Set your Previews to the highest resolution and quality that you might need. (I set mine to equal the resolution of my largest display, with "Quality" set to 10.)
You now have pretty much what you asked for: a trimmed-down Library, RAW Originals off of your system drive, and the ability to create fairly large, high-quality JPGs of your Images at any time.
The next step -- should your Library outgrow this set-up -- is to put your Library on a fast external drive. External drive throughput is excellent today. Start-up time for a Library on an external drive is slower, but once loaded a Library on an external drive should appear to the user no different than a Library on an internal drive.
The above makes up your _working copy_ of your Aperture system ("system" = Library + Images' Referenced Originals). For backup, make two copies of your _working copy_. Store one off site. Never have all three in the same physical location.
The Preview is, as you've noticed, a good "extra" back-up of your work. Just be aware that it is a JPG, and is likely lower resolution than a new file created by exporting an Image.
Lastly, you might re-consider using optical media for archival purposes. I looked into this three or four years ago and concluded that keeping two copies of my digital archive on hard drives was less expensive, easier to maintain, more reliable, and gave me far more latitude for storage and retrieval.
HTH,
--Kirby.
Message was edited by: Kirby Krieger
