If you need to isolate a small object on a white background,get it as good as you can in camera, then in photoshop, mask the object carefully, the Image>Adjustments>Levels - select the white eye-dropper and click on the background-"Voila" instant white; if it isn't as perfect as you want it,setdodge tool at 50% soft brush for the large open areas,then reduce this as you get closer to the object, down to 2% for round the edges of the object,remove the mask-perfect isolation.

regards, Grizzlybear