@Harmy: 18 is above the high end for DVDs (SD sources are 19 at the high end, 21 at the low end).

There's a difference between my watching it from a file on my PS3, and keeping a copy of it on disc. I'm keeping a full-blown direct copy on disc. But I don't need all the file conversions of all the movies in my entire library to be fricken huge in size. I just don't have the hard drive storage space for it.

Given that you, Harmy, are so intimately familiar with all the nuances and details of the film's picture quality, I'm sure you could point out any differences. But I'd bet real money that setting it to 21 for a Bluray would make most people (even most people who frequent this thread) hard-pressed to tell the difference, especially any differences which come anywhere close to remotely meaningful.

EDIT: I'm not saying you wasted your time with being so meticulous about the HD quality picture, nor am I saying that AVCHD is perfectly good enough to make the Bluray version moot. I'm saying is that 7.9GB for the AVCHD alone--nevermind 13GB for the main m2ts on the Bluray--is a lot of MKV to deal with for just one film when one has dozens of others which are similar in size. I'm saying nothing about the (obvious to me) need and importance of having a full-blown HD copy on disc.