I'm not sure I can answer how response times are measured - it's done internally. For what it's worth, those specifications have to go through a lengthy process to exist - and that's what we rate the panels at.
While processing may cause a "lag", this is true with any processing on any television. The purpose of the processing is to improve the picture, and doing that can result in varying degress of "lag", and depending on the game and/or user, could be insigificant, or very significant. I have seen some of what some people might call "nitpicks", but I think it's legitimate if it's affecting the gameplay - and the reality is that improving the picture requires processing, which requires time.
Game Mode does reduce a lot of the processing, but there is still an upconversion to 1080p (regardless of the signal) and to the Hz of the panel, in this case, 120Hz. I simply don't have a mathematical breakdown of each processor, or how long it takes to do what.
So here's what I would suggest - take your game station in the store and try it out on the store's display. See if it offers the response time you want with the game you think will be most taxing. Even if I did have all the numbers, at the end of the day, you'll want to know if the panel will do what you want it to do. It's impossible for me to confirm or deny if it will work for you.
Soon, I am planning to purchase a television and have been narrowing down my choices, quite sure on a few models by Samsung.
I have a few issues however.
I am wondering how response times are measured for Samsung models, particularly for the LN46A950. I understand what response time is, I think anyway, but perhaps not, and I know that this particular model is clocked at 4ms. But this number is meaningless to me because of the context.
Is this measurement taken with all post processing turned on? Is it done with only some of them turned on? Or is it minimalistic as in, this is the maximum response time the television is capable of with all processing effects turned off or low? I plan to play games primarily on the set, and am also concerned about the Local Dimming effect taking some kind of toll on the response time as well. I have heard that 8ms is acceptable for games, and am wondering if I can expect this, at least, or better yet the quoted number for the set with Local Dimming turned on, or if I will have to turn most things off and play with the bare image, 3000:1 contrast ratio instead. This is important to me because I do not want to purchase the television if I cannot reap the benefits which up its price tag. I have heard with other LCDs, the processing effects must be primarily turned off or else there will be unacceptable amounts of lag, unsure on if these are simply nitpicks or if there really is some debilitating flaw in the picture which causes ghosting or something, and that this is why there is a Game mode. I couldn't find the specifics for the Game mode of the LN46A950 and so don't know if this setting includes the local dimming, and if the other processing effects, which might be pertinent or enticing to pretty up the picture for a video game, would harm, inconvenience, or destroy my experience with it.
I very much appreciate you time on this issue.