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[filmscanners] Re: archiving scanned images to DVDs



The view on RW media has flip flopped several times.  I have always
believed the technology use din RW media is superior to that of the "R"
media., and some agree with me.

Here's how they differ:

"R" (write once) media has a dyes layer which is burned off by the laser
  to crete on or off bits.  The dye, like all dyes, is sensitive to
light, heat, UV, and just general degeneration.  Each time it is read,
it is again exposed to light.  If it is left in bright lighting, it can
fade.
Further, recent articles I have read indicate that unwritten CD-R disks
may become unreliable in as little as 18 months after manufacture (even
before being written).

RW technology is different.  It is based upon a concept called "Phase
change"  There is a layer of material in that disk that is heat
sensitive.  The heat of the laser, rather than bleaching a dye, "melts"
the layer and causes it to change phase from transparent to opaque.
This is a very reversible process, Each time the laser heats a spot, it
reverses from one phase to the other.

It is not sensitive to ambient light or UV, and the temperature required
to make the phase change is relatively high and concentrated.

Any disk will be lost if it is heated too much and warps or
dimensionally alters.  In theory, phase change technology should remain
stable for many years.  I used to use a phase change product which was
the precursor to RW technology.  hey claimed it could be rewritten up to
10,000 times and had a 35 year shelf life.

RW technology has the speed pre-written into the disks, unlike "R",
which can be written up to the limit of your system and their
reliability levels.  So, RW disks are rated for their highest level, and
you can't push them further.  If they cannot be made to write at their
rated speed, it can mean your system cannot support the write speed, due
to CPU overhead, speed of harddrives, or busses.

I am still new to DVD, so it might depend upon the type of data being
recorded, as to the speed the system can write at.  I'm guessing here.

Art


snsok@cox.net wrote:
> It's time to archive about 10 gb of images from the hard drive.
>
> I mistakenly purchased a box of DVD+RW discs rather than the DVD+R discs. I 
> recall there was an issue with CD-RW media not being as durable as CD-R 
> media. How about rewriteable DVD media? Does the same difference hold for DVD?
>
> Also, second question.  I purchased an 6X DVD drive. When writing 
> photographic images to my current media, rated at 4X, the actual write speed 
> varies between 1X and 2X. Is that related to writing image files? My files 
> are mostly TIFFs with some Photoshop PSDs.
>
> Stan Schwartz
>
>

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