As an avid photographer, you know that storing your digital photos in only one place such as on your computer hard drive is dangerous. Many people back up images on CD-Rs for protection in case of a major computer crash. If duplicate CDs are stored off-site, we’re also covered in case our home is lost or severely damaged in a fire or storm.

Since CD-Rs range considerably in price, is there any difference in quality? What difference in performance and archival life can we expect when comparing cheap discs to more expensive ones? This month we’ll look at the differences among CD-R discs.

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.

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.

But with any type of disc, here are some tips that will 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.

2. Store discs in a cool, dry area and position vertically to prevent warping.

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.

4. It’s safer to print directly on CD-Rs that have a printable coating, than to apply labels. Bubbles and delamination of the label may cause the disc to become unbalanced, with resulting errors in high-speed readers.

5. 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.

6. 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.

We Have A Winner!

Congratulations to Gary Metsker for winning the
Porter’s/Tamron May 2007 Monthly Calendar Photo Contest! Gary’s winning entry in the “Tiny Tots” category is ready for downloading as a 2007 monthly calendar at www.porters.com.

Visit our web site and check out the monthly themes for the rest of this year and send us your best shots!