ImgBurn doesn't give me back the same ISO I started with

[wylbur7]

I recently took an ISO file and burned it to a CD using ImgBurn.
Sometime later, I decided to read the ISO file back from that same CD
using ImgBurn and check whether it matches the original ISO.

I noticed two unexpected things.
When I asked ImgBurn to create the image file, the default filename
was "Image.bin" instead of one with an ISO extension.
When I changed the extension to ISO, it says ...
  ISO is not an appropriate container format for the current disc
  but I will make the necessary adjustments (convert MODE2/FORM1
  to MODE1).
When it finishes writing the image file, I find that
it's not even the same size as the original ISO file.

If I started out with an ISO file, and used ImgBurn to write a CD
from that ISO file, then why doesn't ImgBurn give me back
the same ISO file I started out with?

...
 

[LIGHTNING UK!]

You should have posted logs.

 

Your original image shouldn't have been an ISO.

 

As for the size difference after conversion... Well I can only assume your drive padded something out. Again, we need the logs.