Use the tripod and set the timer....

...that way the camera doesn't move with the shutter open as you release the button.

Another thing you might want to try is change the EV value. When I shoot on white, I usually set the EV at +1.

Experiment and see what happens when you shoot pics at -1, 0, and +1 and +2 on you camera. You should end up with something like this:



Also play with the white balance settings. You should end up with something like this:



This is what a photo shot on white should look like:



Alternately, when shooting on black backgrounds, go to EV=-1:



I hope this helps,
Val