How Blu is that Disc in the Player?
Blu-ray is touted as the next-generation of movie watching at home because it provides a high-definition picture, but it actually has a lot of similarities with good old DVD (besides being a disc with a hole in the center that is). Like a DVD, the picture coming off the Blu-ray disc didn't just magically appear. Engineers and other professionals were responsible for turning the movie into the digital technology "living" on the Blu-ray disc. It's that process that can make or break the overall quality of what you see, regardless of it being an HD picture.
The Men Behind the Disc
There are a number of factors that affect the overall quality of the recording being put on the Blu-ray disc. For one thing there's the quality of the original used to make the copy on the Blu-ray disc. If the studio uses the best original possible, the copy will be a better representation than if the original used is a 2nd or later generation. This becomes even more obvious in the case of older films where all that's left are poor copies to work from. This isn't helped along when the studio doesn't give the needed time and attention to making the best possible digital master of the film first.
Encoding Till The Discs Come Home
The next factor is how the original is encoded onto the disc. There are a number of different video encoders to use, and there seems to be a bit of a subjective bias as to which one is best. So while the video encoder VC-1, for example, might work excellently for movie X, while being a poor choice for movie Y, there's no hard rule that says "go for VC-1." Who knows? Maybe using the AVC video encoder for that particular movie was the solution.
The final factor is all about being human. A real, live person, not a machine is responsible for seeing that the film makes its way onto the disc in the best possible fashion. Or should. This professional engineer should be making sure that the compression that is required in order to crunch that film onto the Blu-ray disc isn't causing issues with what is being seen. Like overworking digital noise reduction or creating artefacts and other visual guffaws. Professionally mastering a Blu-ray disc takes more than just a sure hand and knowledge, it takes someone with an instinctive feel for how to coax the best out of the technologies at hand. Not every person given the task will perform as well as another. Which will be borne out by the results when the Blu-ray disc starts spinning and everyone starts watching.
The Personal Touch
Finally there's the extreme bias of one person over another. If you really love a film, watching it on a Blu-ray disc that isn't completely up to snuff is okay. Because it's your fav. You'll "give it a break" because you're so fond of the film that it doesn't matter. Though of course it does. Until robots start doing Blu-ray disc reviews, we'll all have to acknowledge that there's more to the "eye" than just cold hard technology. That doesn't mean giving a free pass to studios who fudge their Blu-ray discs. It just gives them a couple more tries to get it right.