Matt, Generally compression isn't recommended for a few reasons. While Zip and LZW are fairly reliable compression algorithms, they add another layer of complexity to the file. It's possible that the compression could make unpacking them more difficult down the line. I've heard it suggested that this is particularly true if there is some bit level corruption of the file, which could cause the compression to fail. (comments from people who get under the hood with files would be appreciated...sometimes I feel like these are digital urban legends). I'd be interested in seeing any hard data on this.
The other concern is over the patents held on both compression algorithms. There was a time where the patent holders were attempting to claim control over the patents, suggesting that you'd need a license to unpack your files (or least the people making the software you use would). These mostly seem to have gone away, but the patents are still out there. Generally this is why we've steered away from proprietary formats towards open standards. Richard Urban Graduate School of Library and Information Science University of Illinois at Urbana-Champaign [email protected] -----Original Message----- From: Matt Morgan [mailto:[email protected]] Sent: Tuesday, November 29, 2005 10:39 AM To: [email protected] Subject: Re: [MCN SIG: Digital Media] Uniiversal Photographic Digital Imaging Guidelines Newman, Alan wrote: >Curious coincidence. I just distributed this link today to my staff and I was preparing a post to MCN-L. We've adopted most of these guidelines in my division at the National Gallery. > > I'm curious to know which recommendations you haven't adopted ... let us know! I read through the UPDIG recommendations and found it really interesting and helpful. I thought their recommendation for RAW format was relatively unconvincing, though. Almost like they were saying "we want to recommend RAW format, but we realize you're going to convert them anyway, at least until the DNG format is widely-supported." Their best arguments for RAW applied to oddball cameras--which to me is an argument not to buy an oddball camera. Is anyone behaving differently, and storing files in RAW (but not also storing in TIFF)? I think, although I'm not sure, that the UPDIG Working Group has more faith in RAW than the museum and library worlds do. The other question I've been asking myself a lot lately, but haven't seen addressed much, is why not store files with some form of reversible compression like zip (or gzip or bzip2)? UPDIG doesn't address this (although it allows that compression is valuable and acceptable for delivery). ZIP (and bzip2 and gzip) is perfectly reversible, and it's tried and true. Why store 100Mb TIFF files when we could be storing 10Mb tiff.zip files? Has anyone out there opted to use reversible compression in digital repositories? If not, why not? I realize that JPEG2000 would also solve the compression problem, but ZIP ought to have less of an acceptance problem than JPEG2000 (as ZIP is already so established). Thanks, Matt --- You are currently subscribed to mcn_mcn-l as: [email protected] To unsubscribe send a blank email to [email protected]
