I heard that 1620 produces less rings compared to NEC. (In fact, NEC at CLV will always produce small color changes, I believe.)
Nevertheless, even BenQ is not a ring-proof drive. I sometimes see it.
It is mainly due to the active WOPC such as laser power change, write speed change, etc. Not having a ring at CAV or PCAV is a good sign, I think, because it means the dye is very clean and regular.
Sometimes a ring region reports high PIE and PIF scan, I take it a bad sign. But it doesn't mean rings solely distinguish a good disc from a coaster. Here's one scan I used for a previous thread. This disc has a faint but visible ring at the outer part. Can you even see where it exists?
Too many people buy the "ring theory" or whatever.
Even Gollum may say you guys are "obsessed" to the precious(?) ring. :bigsmile: