: I am about to archive images to optical media and in light of recent debates : surrounding the issue of CDs x DVDs in terms of reliability I decided to do : some research first before choosing the media for the job. : : Although I've done some basic research on the internet it is hard to know : what sites provide reliable and trustworthy information that can be fully : trusted. : : Do any of you have information to share on the benefits of using CDs and : DVDs as long term storage media ? Which one is the best at this time ? I : understand CDs are more "universal" and the data is not quite as compressed, : but since DVDs are tempting due to their much greater storage capacity in : the same physical space, I would like to know how reliable they are (more : error prone than CDs ?) and how long they are expected to last compared to : CDs. : : Do you have information on the differences between the two media ? Would you : suggest any specific web site that offers detailed and reliable informaition : on the subject ? a collection of some some stuff I posted before: DEFINATELY look at kprobe (listed below).. from CDMedia world - the goss on TDK's.. some of which are even MADE by TDK <!?> http://www.dvdmediaworld.com/hardware/cdrom/tdk.shtml and other brands.. http://www.dvdmediaworld.com/hardware/cdrom/dvd_info.shtml some stuff about quality http://cdmediaworld.com/hardware/cdrom/cd_quality.shtml and dyes.. http://cdmediaworld.com/hardware/cdrom/cd_dye.shtml the most durable dye, PhthaloCyanine, used in Princo's is also used by many other makers too but I see the TDK's listed here are using cyanine (what!!!) - the worst dye of the lot for longevity - and they use this in the disks that they guarantee for 100 years even tho the dye's only expected to last 10 years. OK, they don't list the dyes used in ALL the TDK's but hey - something funny going on here :-/ the latest APC (aus computer rag) has just done a nice little article on CD 'rot' - on the degradation that affects optical media. I won't write out the article in full but I *will* rip it to a pdf later and make it available online in the meantime here's some of the info they came up with. Note that they tested 14 spindles of disks from each of various manufacturers so the results are indicative only,they could of course have bought bad batches.. but they DO explain how they tested and they went into a reasonable amount of detail about how and why CD/DVD media fails. I still believe stuff like this should be intensively covered in ANY course that purports to be teaching folk about 'digital' photography, as it's a fundamental to computing, just as aperture and shutter speeds are fundamentals to photography !! The author emphasises the NEED for folks to run their own tests on their own bought batches and suggests a number of programs and methods available that can do this, but they also caution that really thorough testing can be prohibitively expensive and recommends folks keep an eye on the various forums (such as the ones I've listed previously) for up-to-date information. They also say that companies regularly change manufacturers, factories and production lines so expecting consistency from any one brand is a really stoopid thing (!) on to the results. things measured: the 'BLER' - the block error rate E22 & E32 errors - unreadable and barely readable errors Reflectivity - should be higher than 65% WAWM - combining 36 timing variables inc jitter into a single value. I wont tabulate all the results, but here is their ranking based on tests Rank Brand BLER average 1. ProDisk Premium 0.1 2. BASF digital audio 0.3 3. ProDisk Dub Utility CD-r 1 4. That's CD-r 80TY 700Mb RV 0.3 5. That's CD-r 80TY 700Mb Taiyo Yuden 0.9 6. HHB CD-r74 0.6 7. Imation CD-r 700 2.1 8. Sony Supremias 2.8 9. EMTEC CD-r 3.5 10. Laser 80 min Premium gold 9.3 11. TDK 74 min printable 33.2 <-- hmmm.. 12. Verbatim cd-r 9.9 13. Sony CD-r 700M 378.6 (eek!) As i've said in the past, the dye type and longevity is also a factor, one they've mentioned but not considered in their test results preferring to merely state the dye type, and again TDK comes up as using the lesser cyanine. others such as the 2 nd TOP performer in this list do too, so again lists like this can only be a guide. As you're all probably aware - I've been advocating DVD's over CD's for a while. I recently pulled apart the laminates from a bunch of DVD's and found the laminating process from disk to disk looks like it was done by trained monkeys on their day off after a hard night on the town :-( Laminated disks offer dimensional stability WAY stronger than CD's, but hey.. if the damned things delaminate in the DVD reader you'll be picking shards of plastic out of your walls for days, never mind thinking of data recovery! Ok, that's a bit extreme.. they're not that likely to separate under use, but by delaminating they ARE exposing the reflective surface to oxidation and thus degradation. A simple solution however is to seal the edges yourself! :-) This can be done by simply running a tiny bit of nail polish *carefully* around the outer and inner edges of the DVD and allowing it to dry - bingo, sealed :-) If you don't have a clue what I'm talking about then I suggest you grab a cheapie DVD-r and really look at it. You'll see it's made up of two disks stuck together or 'laminated'. Poke a fingernail in between the two and you'll be able to peel off a clear plastic disk, leaving a shiny aluminium surface covering the dye on the bit the DVD reads. Have a look at how the layer was glued together. that's it - whatever you see in the way of dobs of glue, faint thin glue lines or whatever, that's what's keeping the air and moisture out - if you don't like what you see then go nuts on your other disks with the nail polish. www.DVDrecordable.org - a good site for reviews on optical media and drives and http://www.dvdinfopro.com/ - DVDINFOProT by Nic Wilson is a DVD information program written in Visual C++ for Windows 95, 98, 98SE, ME, NT, 2000, XP. Will tell you how good your burner is and how good the media is ************************************* kprobe: from http://www.cdrlabs.com/kprobe/index.php (2.1Mb download) allows you to test dvd media by looking at the errors on the disks. ************************************* http://www.videohelp.com/dvdmedia princo AND TDK DVD's (and others) scored a GOOD rating, interestingly there are substantially more user comments, most very good, on Princo than the nest nearest commented upon brand.. 297 V 74 comments seems that the reviewers also get to state how many disks they've burned too - some of the reviewers have burnt a mere _single_ disk on which they've based their reports - the Princo brigade however all seem to have burnt 25, 100, 50 etc . I think the *best* way to resolve this is to check the error count on the various disks available and then treat the results as a guide*. As is stated there, compatibility is NOT a good guide to reliability, only the error count gives a true indication of fallibility. *as with film, every batch is different and because one review says their lot tested good doesn't mean the batch I buy tomorrow are also going to be as good k
