Whats the difference between a Pressed DVD and a burned DVD

[baritony]

Hello. Now I know what a pressed DVD is - a DVD you buy from the store, and a burned DVD is one you(we) do at the consumer level. But what is the real difference in them?
How is it done? Is there different media?

Im looking for 'real' answers eaning techincal answers if anyone can help, thanks

[angelog22]

Try this thread.

https://www.videohelp.com/forum/archive/t135046.html

[MOVIEGEEK]

Basically a pressed DVD is a metallic film that has the data "pressed" between two or three layers of polycarbonate.A DVDR blank uses an organic dye that is squirted in between two layers of polycarbonate and spun to spread the dye.
A DVDR will never last as long as a pressed DVD no matter what the manufacturers say they will(99 years).

[solarfox]

The difference is exactly what it sounds like.

"Pressed" discs are stamped out in a plastics-molding stamper. The data patterns, represented as a series of pits and lands (a "land", BTW, is simply the absence of a pit in a particular spot), is permanently molded into the plastic during the stamping process. Basically, its the same process that was used to make vinyl records (and CD's, for that matter), just ramped up a few orders of magnitude in precision. After the plastic has been stamped, it then gets coated (via vacuum deposition, if I recall correctly) with a few-atoms-thick layer of reflective metal, and another layer of plastic is bonded onto the top. During playback, the laser's reflection angle is subtly altered depending on whether there's a pit or a land in front of the beam, which causes the reflection to hit or miss the detector. These hits and misses become a binary data pattern.

"Burned" discs, on the other hand, do not have the data permanently embossed into the plastic. They are produced similarly to a pressed disc to start with, in that they are molded in a plastics stamper, but instead of a pattern of pits and lands representing data, a pattern called the "pregroove" is stamped into the plastic. The pregroove's primary function is to give the write laser something to track as it writes the spiral data pattern from the inside out. In between the bottom layer of plastic and the reflective metal layer, there is a layer of photochemical dye which responds to a particular frequency and power of laser light. During the write process, the drive actually does "burn" the dye, causing it to become opaque in spots where the laser hits it. This pattern of light and dark spots then mimics the pits and lands of a pressed disc during playback, by blocking and unblocking the laser reflection. (The detector doesn't know if the beam isn't returning due to a dark spot or an altered reflection angle, all it knows is it doesn't see the return beam.)

[baritony]

Excellent! This is exactly what I was looking for! Thanks guys!!