Hi TANGUYEN,
I edit videos for a living, but first an explanation of what your experiencing:
Remember, because the footage you shot on your camera is digital and it is then transferred to your computer digitally (firewire I gather?), the information is exactly the same I.E. the picture and sound on your camcorder is exactly the same as what is on your computer.
The trouble you are having is what many people experience - the difference in screens. There is a difference between your camcorder screen and the computer screen. Your computer screen could be set to darker whilst your camcorder screen is set to lighter.
Firstly, your camcorder screen should never be brightened - it should always be left at a standard / middle setting. This way you see what you are filming - not a falsely brightened image. Look in the manual to work out how to change the screen's brightness.
Secondly, your computer monitor should be set at a standard / normal setting. It should have some settings somewhere allowing your to put it in standard preset modes or reset it or something.
Thirdly, view the output image on your television in its standard brightness setting.
NOW. If this hasn't solved your problem, you can brighten images in most editing programs however do this with caution as the more you digitally brighten the image, the grainer the image gets.
The good news is that at least on one screen you can see the images properly - meaning that the information is there, it might just need some tweaking.
If you need a hand, I edit videos for a living and can help you out. I could do some of the fixing for you or even give you an intensive workshop into editing so you can do it yourself. My classes are particularly aimed at HSC video students. Contact me via email
writers_blok_productions@hotmail.com if you feel you need a hand.
Good Luck,
Chris.