FACTOIDS: LASER & MEDIA ISSUES (DVD9 Added)

[charlie_ps2]

I've reposted and update this info as many new members won't have seen it and there is some new info since it was first posted.

Many people think that burning CDs at 1x or 2x is best; others report good results at higher speeds. Here is something fairly technical that I hope you find useful.

I'll use Verbatims as the CD-R example. They come in three subtypes within two types of photosensitive dye:

Cyanine
Datalife Plus
Metal AZO

Pthalocyanine
Datalife

Cyanine CDs have a Long Write Strategy and so burn best at 1x or 2x. They have a longer shelf life if exposed to light, especially AZOs.

Pthalocyanine CDs have a Short Write Strategy and so burn best at 4x or on the best burners 8x (Laser power matters at higher speed). They have a shorter shelf life if exposed to light - say 10 years.

With CDRs it's all about ensuring that the burned opaque bit doesn't splay so as to make it difficult to read; burn a Short Write Strategy CD-R for too long and that's what happens. Pressed CDs have clean pits and ridges and it's the transition from one to the other that counts as a 1 bit.

A CD is written/read along a spiral groove which is tracked by the laser. Light is reflected back to the laser's optical diode and phase difference is measured between sent and received light.

Plextor & Yamaha (and possibly other) CD burners use a mechanism called Running OPC to vary laser power and speed according to information decoded by the reflected light coming from the groove. The aim is to make the opaque burn as clean and unsplayed as possible, thus making the CD-R the closest in optical behaviour with a pressed CD. With such burners, it is possible to set a higher speed than what has been suggested above because appripriate (more) laser power would be applied at the higher burn speed.

Bottom Line
If you were aware of the above and burned at the said speeds, then you would be satisfied with the results. PC World (UK) "unbranded" media are the same fabrication as Verbatim Datalife (except that Datalife have better surface protection), and these both are the ones I rate best.

As ever, my advice is taken at your own risk!!