I've found this to be true with both taking pictures with a camera and using the keyboard. It is not the initial touch or push on the keyboard or camera button that activates the key selection or camera, it is the release of the finger from where you touched.
With the keyboard, that's really neat. It means you don't need to use 3 keystrokes to move from alphabetical to numerical and back to alphabetical. You can touch/push the number selector key and drag your finger to the symbol or number you want and then let go and the number/symbol will be selected and you'll be back in alphabetical keyboard immediately.
An Apple Store instructor the other day showed the camera suggestion to me: Click/push the camera button and hold it until you have the picture you want in the viewer and then lift up. The camera takes the picture then, when you and the object are not moving and without the lag time problems. Seems to work better.
