I was wondering if someone could answer an annoyance I've had for a while when using brushes with PS.

I made a few forest brushes out of multiple tree brushes but when I place these brushes the sharpness of the resulting image can differ immensely. I have every option turned off in the brush dialog, so I have no size jittering, opacity changing, wet edges... nothing. But if I place the brush 10 times I can get 10 different images, ranging from pin sharp to looking like it's had a 1px gaussian on it.
I would have thought, that with all controls of the brush turned off then it would repeat exactly the same every time.

Does anyone know why it doesn't? And more importantly, does anyone know of a way I can make it so that it does?