Message-Id: <mailto:199505081439.JAA10589@library.wustl.edu> Date: Mon, 8 May 1995 10:18:45 -0400 From: Joel Wolfson <mailto:DigiWolf@AOL.COM> Subject: Re: digital image tape storage To: Multiple recipients of list IMAGELIB
To: mailto:troncale@NYPLGATE.NYPL.ORGRegarding your request for information on storing hi-res images on tape:
Most of the images I store range in size from 20 MB to 100 MB. I use DAT tape. I always make two copies of everything, that is on two tapes in case one should fail (and I have had them fail). I use Retrospect software. It doesn't have the most elegant interface but it has extensive search and retrieval options and is a standard for Mac based DAT storage.
Compression is a two edged sword. It provides much faster backup times and usually allows at least 2 or 3 times the amount of info on a tape (about 5 GB on a 90m tape). I'm referring to hardware compression built into the DAT drive, which is lossless compression. JPEG or other lossy types of compression are a whole different story. The drawback to hardware compression is compatibility with others outside of your own facility. The only standard established in DAT hardware compression is DDS-2 which is great as long as the person who is accessing your tape has it. I avoid using non standard hardware compression except for internal use only.
If your purpose is to archive images, make sure you have plans in place to transfer all your archives every 5 to 7 years to a current storage technology. And keep in mind tape's lifespan is about 10 years (vendors will tell you 30 years but don't count on it).
As for file format the most universal for images is probably TIFF. If you want to use "lossy" compression then JPEG. If you haven't used JPEG before make sure you experiment with different levels of compression on several different types of images. Be especially careful of images with large areas of one tone/color- they suffer most noticeably with greater amounts of compression.
If a wide variety of outside users need access to your images you may want to consider a CD ROM writer to create your own CD ROM's. A good unit is more expensive than a tape drive but anyone with a CD ROM drive can read it and it's a much bigger standard that DAT, Exabyte, or the numerous other tape formats.
Hope this helps.
Regards, Joel Wolfson DPI Manager Digital Photographics & Imaging a division of West Photo (612) 379-2321 Main (612) 699-2533 Direct E-mail: mailto:digiwolf@aol.com