copy form gerti67 post (with his authorization)

see the fantastics results using "levels":

"The picture in the middle is the original dark scene,
on the left is the picture with the "Tweak(0,1,20,1)" setting
and on the right is the one with the "Levels(0,1.3,255,0,255)" filter.

Decide for yourself which you prefer.
But you can easily see the difference.
The black bars stay black on the right one.

Greetz,
Gerti"

http://free.pages.at/gerti67/pictures/tweak-levels.jpg

thank you very much for this special link, your attention
and great explanations Gerti

Looks good jorge, the only bad thing is that most likely you gain file size.
You have to give a little to get a little.

yes Osvaldo,but just a little.
if you use luminance filter(gain and/or offset) in dvd2avi
or tweak,the size will encrease too.

levels give better results!

That's because you are comparing two different things. With the Tweak line you are only increasing the brightness, meaning black gets less black. With the Levels values you are changing the gamma value, which is not possible with Tweak.