how responsive is the iOS screen?

I'm experimenting with my ipad as a music controller, and finding that there's too much latency with touchesBegan events for it to work we开发者_运维百科ll as a responsive-feeling percussion controller.

Am I doing something wrong, or is this a limitation of the devices. Which factors effect the amount of time that elapses between my finger touching the screen and the touchesBegan event firing?

It is much much less than 250 ms. I experience in the range of 25 - 50 ms for most events on the iPad -- which, unfortunately, is only fast enough to coarsely represent events on the scale of percussion. Sure a percussionist usually doesn't diddle 20 times a second (sometimes they do) but even if they don't, sampling theory explains why the iPad (or any of its late-to-the-game contemporaries) can't represent the timing accurately.