I was searching for definitive information regarding the difference between the two formats of writable BluRay media, and found a bulletin from Verbatim which explains a lot.
It's on the web as a PDF, so I thought I'd share it here in case they ever remove it because it's a nice clear explanation.
I had to break it in pieces to keep the file sizes in range for this site.
original link: BD-R LTH type Product introduction
https://www.verbatim-europe.co.uk/includes/binary_details.php3?id=7040The wording of the first page past the title page is as follows:
What is BD-R LTH type?
• It is just another type of BD-R, specified in Spring 2008 by Blu-ray Disc Alliance
• Recording layer is different:
• First type of BD-R is made of inorganic material
• Signal changes polarity from High-to-Low (HTL)
• AZO BD-R is made of organic material
• Signal changes polarity from Low-to-High (LTH)
• BDA states mandatory use of wording „BD-R LTH type“on packaging and disc label