[CS-FSLUG] ISO Image Quality & Burn Speeds

[Steve McCracken]

Brian Derr wrote:

>>When I ran the installation on the slower, target box, I
>>got an error message suggesting I burn at a slower speed.  I don't know the
>>cause - whether it's the Verbatim media, the burner (possible rotten apple
>>in Sony's bushel), or the target drive.  The target box is a custom 300MHz
>>box.
> 
> 
> It could possibly be the old CD-ROM drive in the target machine can't
> read CD-Rs very well as they came after the creation of the drive.
> There are audio CD players that are years old that cannot read burned
> CDs so I would not be surprised if there are CD-ROMs that don't have the
> same problems as well.  I don't understand how the speed you burn on the
> host machine has anything to do with the read quality on another machine
> though...

It has to do with the process of making the different CDs.  The pressed 
CDs (original, non-burnable CDs from manufacturers) have a high 
reflectivity for the laser that reads them.  The CD-Rs have a lower 
reflectivity and the CD-RWs have even lower reflectivity.  Therefore you 
will find (especially in the older drives where they can read pressed 
CDs but not the other two types.  It also explains why some read CD-Rs 
but not CD-RWs.  Cleanliness of the lens and alignment of the lens/laser 
also affects things.  I agree with you that the speed of the burner 
doesn't affect the ability to read on another drive.
> 
> 
>>What I do know is that slower burn speed seems to equal better success.  The

The amount of time the laser spends on turning the bit from a zero to 
one (or visa versa, I can't remember) obviously will affect things. 
When you burn it slower, the laser has more time on each bit to effect 
the change, so the burn will have a higher probability to come out as a 
high quality burn.  Many recommend for archive quality burns to burn as 
slow as possible.

As someone once said, CDs are indestructible unless you treat them that 
way.  Radial scratches are not as problematic as the scratches on a 
tangent.  The error correction can handle small bit loss, but a 
tangential scratch affects many more bits.  Also, think about how you 
handle the label side of things.  If the label side is damaged enough to 
let air reach the burn layer, it can also begin to deteriorate the CD.

>>image is installed now, so it's kind of moot.  However, I am still open to
>>suggestions.  Once I swap this old 300MHz box back out for my swap box, I'll
>>be looking to play with installing Slack, Gentoo, etc. on the swap box till
>>I need it again.  So I'll probably burn a few more ISOs.
> 
> 
> MMmmmm, Slackware, my first linux love.