>We are creating a digital collection by scanning transparencies onto CD. They >are jpg's that become part of an educational collection accessed on-line from >an Inmagic database. Is there any loss of quality to the database copy when >they are viewed on-line? If there is, would an archival master saved to CD be >adequate back-up? Well, the jpeg format is a 'lossy' one, meaning that it loses data when initially created. The way it creates smaller files is by averaging out little areas of pixels. However, there is a sliding scale of quality that you can use when creating the initial jpegs - it's a compromise on compression size versus quality. The more you compress the file, the greater the loss in quality. If you're really curious about the jpeg algorithm, fire up your favorite image editing application (photoshop, paintshop, gimp, etc) and really zoom in on the image. You'll start to see little chunks of blockiness which is the joeg algorith at work. Now, going back to your original question. It sounds like you're asking if the jpeg will continue to lose quality through repeated online viewings, and the answer is no. When someone looks at the jpeg through a web browser, the web browser views an exact copy of the jpeg at the quality at which it was originally saved - there's no additional compression that would further degrade the quality of the image. And, it shouldn't alter the jpeg image already in the database; web browsers are read-only devices for what we're describing. It sounds like what you're doing is probably fine. However, if you're concerned about losing some quality by creating jpegs in the first place, a reasonable alternative approach is to save two versions of the file. The first, a lower resolution version, would be the jpeg that you're already creating, or maybe at an even higher level of compression. The second version should be saved in tiff format with compression. The tiff file format doesn't discard any data when it compresses the file. It works through looking at the bits in the file and looking for repeating 1s and 0s and mathematically crunches the image. No pixels are touched in the process. Make both versions available, with the realization that the higher resolution tiff is meant for download rather than online viewing. Of course, making higher resolution images available may not be something that's desirable to you because it enables better reproduction, but the discussion about copyright and digital watermarking should be saved for another day. Good luck. Hopefully this answers your question. -bw. -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Bruce Wyman e: <[log in to unmask]> Manager of Creative Development v: 617.491.3184 Nearlife f: 617.354.4191 147 Sherman Street, Cambridge, MA 02140 w: <http://www.nearlife.com/> ========================================================= Important Subscriber Information: The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes). If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).