Hopefully this isn't considered hijacking, but I think there will be very similar performance between the two so...
While I can't speak to the 40, my RS-50's lag time is at least
200 ms in THX mode, and 'feels' around 80-100 ms in other modes. This is with no CMD, extra processing, etc.
You've read right, there's almost a quarter second
of input lag in THX mode. It's so bad in fact that lip sync is noticeably off on DVD's and Blurays from my Sony BD player, as well as movies and TV shows from my HTPC.
As far as why? Good question. I just know that I've never seen lag this bad before.
Before anyone thinks I'm bashing my dear 50 let me say that said I've already grown somewhat accustomed to it, but make no mistake, in all
modes I dare say you may notice a slight delay, regardless of player and AVR settings, and even with using direct from Player-->Projector connections.
In THX mode however, my somewhat extensive testing has shown audio will simply not
sync 100% with the screen action unless using HDMI 1.3 lip sync correction (if available).
For the sake of completeness, my Dell 2410 monitor I often mirror with the projector seems to be rated around 40ms, a speed I've always felt is the upper-limit of what I can start to detect:http://www.tftcentral.co.uk/reviews/dell_u2410.htm
The 50 however, is simply noticeably slower than this.
Current owners will also confirm that syncing an HDMI source is also painfully slow. Often times a TV show's audio will start with no picture for a good 2 or 3 seconds as we switch display modes from the DVD menu screen to the actual episode.
All of that said, I still love my PJ--last night I watched a few minutes of some Pixar films in the Anime setting and it was literally awe-inspiring. I just hope they can address these other issues via firmware. If they don't this will be my first and last
JVC projector. Quality isn't just a pretty image, for these prices it needs to be the whole package!
All that said, according to this site
In 1998, ITU-R published BT.1359, recommending the relative timing of sound and vision for broadcasting. Studies by the ITU and the others have suggested that thresholds of timing for viewer detection are about +45ms to -125ms, and the thresholds of acceptability are about +90ms to -185ms. In addition, the ATSC Implementation Subcommittee IS-191 has found that under all operational situations, the sound program should never lead the video program by more than 15ms and should never lag the video program by more than 45ms ±15ms.
Which to be honest, I find a bit disconcerting. Hopefully JVC has not decided that this and similar findings should be the norm.