I get loads of questions about the archival DVD, so I thought I'd take a minute to explain some tech-y, geek-y stuff about it. When you go to your favorite electronics store (Best Buy for us) you have loads of choices when you go to buy CD's to burn things on. You'll notice tons of options, and sometimes they are on sale. Like the 100 pack for $4.97 the day after Thanksgiving?? That's great and all, but there is a reason it's so cheap. Since CD-Rs range considerably in price, is there any difference in quality? What difference in performance and archival life can you expect when comparing cheap discs to more expensive ones? ------ Warning, this is about to be boring, if you want to skip this part and remain uneducated, scroll to the ********** ------ CD-Rs contain an organic dye layer above a reflective layer. A high-energy laser "burns" pits in this dye layer, forming dark, non-reflective permanent marks. When a recorded CD is played, a low powered laser reads the photos (as well as music and data) as a combination of reflective or non-reflective marks. Reusable -RW discs use a different dye that can be rewritten, but it's not considered as stable for long-term storage. Two factors affect the longevity of CD-R discs, the type of dyes used and the type of metallic material used for the reflective layer, which may be silver, gold or a gold/silver alloy. Three dyes are commonly used in CD-R production: azo, cyanine and pthalocyanine. DVD-Rs use proprietary variations of cyanine dyes. All dyes change in time, including the dyes used to make CD-Rs. The National Institute of Standards and Technology tested optical disc media in 2004, subjecting various disc types to accelerated light, temperature and humidity levels. They found that dye type is generally considered one of the more important factors that may contribute to the stability of the media. Samples containing pthalocyanine dye performed better than other dye types, particularly when combined with a gold/silver alloy reflective layer. Discs containing cyanine dye performed well when exposed to light, but suffered under the temperature/humidity conditions. Discs containing azo dyes suffered under light as well as temperature/humidity tests. And when you write on them with a Sharpie instead of an archival pen, guess what happens, this disc is going to suffer, ie. eventually crap out on you. Unfortunately, finding out what kinds of dyes are used in disc production is not easy, since this information is seldom advertised.
One exception is Delkin, who stresses pthalocyanine dyes are used for their premium line of Archival Gold family of 300-year CD-R and 100-year DVD-R discs. Because I have a slutty trigger finger when I shoot and also because I shoot in RAW, the option of putting decent sized files on CD's versus DVD's is not an option. The DVD's hold more, store more compactly, and there is less "stuff" to lose. ********** If you skipped that boring part, just know that I try to stay in the news about this subject and will always use the best possible preservation method when giving you your images in an electronic format. It might change over time, but there's always going to be a reason. That being said, here are some handy tips to help you extend the life span and decrease chances of errors. 1. Avoid flexing and bending the disc. This can cause tiny cracks to appear that invite humidity problems and cause the disc layers to separate. DVD cases have a push-to-release hub that helps prevent flexing, since DVDs are particularly sensitive to flex problems. And guess what, the cases I use are, you guessed it, archival quality! 2. Store discs in a cool, dry area and position vertically to prevent warping. You can find ways to do this in a fireproof safe or a safety deposit box. 3. The safest place to write notes on a disc is in the clear area around the hub. This prevents ink solvents from migrating into the data. I won't write anythig on your disk but if you do, go to Staples and get archival safe pens. 4. Treat discs with care. Scratches may cause read errors, since scratches diffuse the clear plastic and the laser can't clearly define the non-reflective and reflective areas. 5. To clean a disc, use a CD or lens cloth with a liquid solution containing water or isopropyl alcohol. Wipe radially from the center to the outer edge. Do not use wood-based cleaning products such as paper towels or facial tissue, or liquids that contain acetone. 6. Remember that this DVD I give you is for use in a computer, not the DVD player attached to your television. |