Recreating an ISO File from a DVD-R

[DiscBurner]

If an ISO file is burned to a DVD-R, then recreated as an ISO from the DVD-R, will the new ISO file be exactly the same as the original?

 

Here is what I did:

 

1) Downloaded Linix Mint ISO from http://www.linuxmint.com/edition.php?id=106.

2) Checked the MD5 hash for this file was same as given on the Linux Mint site (using WinMD5Free from http://www.winmd5.com) - it was.

3) The ISO was burnt to DVD-R using ImgBurn 2.5.7.0.

4) Later, I recreated the ISO (just as a test) on the hard drive from the DVD-R, using ImgBurn.

 

I found that the ISO created with ImgBurn in step 4 was different to the ISO I download in step 1 (MD5 hash values are totally different).  Could you please advise is this normal?  Why should both files be different, if the ImgBurn ISO was effectively created from the downloaded ISO (via the DVD-R)?

 

Thanks.

[LIGHTNING UK!]

Sometimes drives will pad a disc so its size is a multiple of 16. So if you burn an ISO that is made up of 17 sectors, the disc will appear to be 32 sectors. ImgBurn would read all 32 when making the new ISO using 'Read' mode.