In order to get really good white balance you have to stop relying on the Auto White Balance function on your camera, you might not realize it now but it probably sucks. A quick tip:
- Put your camera on auto mode and manual focus.
- Stretch said white thing over your lens and take a picture.
- Go to your menu and set manual white balance to the picture you just took.
- Put your settings back the way you had them before and go take awesome pictures.
You may also photograph a subject laying in the light you are attempting to use. The so called white balance is actually a gray balance, so a gray surface appears neutral in its current light, which is being substracted from of the picture.

