Hi guys, I realize that models, with the D50 as the exception, above the D90 have an auto-focus motor built into the camera body, and models below do not. I was wondering if the auto-focus motor differed in quality lets say from the D50 to the D90 to the D3? It would makes sense that there is some small difference that would favor the D3, but is it a large difference? I am just wondering because i would like to know that if the motor in the D50 would negatively effect auto-focus speed for a demanding environment such as sports? As far as i am concerned the auto-focus speed, which is determined by the built in motor depending on what lens one is using is going to be a tad faster as you go up the chain. For example D50 Thanks!