Does the D100 Have A Shutter Lag?
In order for an SLR camera to actually take a picture, the semi-silvered mirror that directs some of the light up to the viewfinder has to be lifted out of the way temporarily, dropping back into place at the end of the shot. The resulting mirror vibration is quite well dampened on current cameras but with longer focal length or macro lenses shot at shutter speeds between about 1/4 and 1/30 second the small amount of vibration might affect the sharpness of your images. Some camera bodies actually have a mirror lock-up that allows you to manually raise the mirror prior to firing the shutter, but alas, the D100 is not one of them.
What it does have though is Custom Setting 24, the anti-mirror shock (mirror vibration reduction) mode. Enabling this function tells the camera to pause for a faction of a second after raising the mirror before actually firing the shutter. This is designed to allow any vibration to subside before it has a chance to affect your image.
This works quite well for those times when you need it, but sometimes people turn this setting on and leave it on, figuring that if it's good sometimes, it must be great all the time. The net result of this strategy is that now the D100 behaves more like a CoolPix in terms of responsiveness. You press the shutter release button and after a brief pause you end up frustrated that you missed the action. But the camera is only doing what you asked it to — remember that this behavior is exactly what Custom Setting 24 is designed to do. New D100 owners that turn this setting on before using their camera much are those ones most frustrated as they have never seen what the camera is capable of. They deserve a better first impression of this great camera.
My recommendation? Turn this setting OFF unless you specifically need it. Leaving it on all the time is just a bit too much of a good thing.