adjust brightness thruout a vhs tape for burning

im trying to get old movies visually the best i can...i got old vhs family movies captured as mpeg2 but to get them half way decent every so often i have to increase the brightness to see some of the darkened footage of the movie then when it comes to a section thats to bright from increasing it from the previuous section i have to lessen the brightness. now, how am i going to get each part the right brightness, thruout a 2 hour tape then burn it to dvd?? is there a procedure, i have videostudio 9.. i have wintv and the brightness was set on its default setting when i captured it and wintv brightness can be changed. so how do i attempt this and should i recapture it again with a different brightness setting or just adjust it in videostudio and how is that done???