However, it is important to point out that there are a huge range of factors that conspire to make Kinect react differently depending on the game being played. Rare's Nick Burton, who we spoke to at the hands-on event, was very specific in pointing out that his game operates with a latency of 150ms, not including display lag.
We've seen in previous Digital Foundry tests on console game latency that 30FPS titles typically operate at 100ms in a best-case scenario. While Kinect Sports can run at 60FPS (certainly the bowling does), the scan rate of Kinect is limited to 30FPS, so at the very best we should never assume to see any kind of response better than the 100ms "standard".
Over and above that there are other considerations. For example, in terms of the lag, there's going to be a fixed "cost" in acquiring the depth map and the RGB info, and there's also going to be an additional latency caused by the transfer of USB - you'd think that these are the baseline fixed costs of operating the system. Then there's the processing of the acquired data, and the different configurations from which developers can access it
So, what are these elements exactly and how would they impact performance? An RGB image with the depth map aligned (or registered, as Microsoft calls it) along with voice command analysis is clearly going to require more CPU work than processing skeletal data and some gesture-recognition alone.
This presumably explains why Burton was so keen to point out that his game operates at that specific level of latency. Even in our own latency tests, we can see an enormous spread of controller lag across many titles running at the same frame-rates and we can imagine the situation being a lot worse with Kinect, definitely in the short term.
As pointed out in our initial hands-on yesterday and indeed way back in the original gamescom Digital Foundry vs. Project Natal feature, the lag factor definitely feels like more of an issue simply because we are used to our actions being transmitted to the console at the highest, fastest level.
Our hands and fingers are capable of extremely fast reaction times, so while jettisoning the joypad may appear to make the games more accessible, the human body as a whole cannot react anywhere near as fast as our brain-to-finger reflexes. This is why Kinect games that, on paper, have the same overall latency as some more traditional joypad games, actually feel a lot less responsive.
Factoring in the inherent latency of human movement is perhaps one of the greatest challenges facing Kinect developers, and what's more this is this is likely to be more or less of an issue depending on the person playing.