setting video effects and restoring defaults

[clamage45]

Two issues:
1. How can I restore the video effects to their default values? The interaction of brightness, contrast, and gamma means that sometimes I want to put one back where it was so I can adjust another, looking for the best overall result.
2. The sliders are very sensitive and difficult to adjust precisely -- a tiny shift can produce a large effect. In particular, the sensitivity of the sliders causes the issue in #1 -- I can't get the slider back exactly where it was. Am I missing another way to adjust the values?