Hello
please direct me to the right forum if I'm in the wrong place!

A friend videoed a concert recently and ruined it using 'night vision' function!

Is there any way to reverse this process?!

Depending on just what camera was used...many cameras use a sort of image "summing" where the frame exposures times effectively overlap and "blur" together a bit.

This process is obviously a destructive one and it can't be reversed. The complete lack of color information in such footage is also something that really can't be rectified.

Sorry for the bad news. I know on our family camcorder (a very small Sony) I always remind my wife not to accidentally hit the stupid "nightshot" button which is right on top of the camera and grouped with many other frequently used controls.

You can't add the sugar after the cake is baked. The best you can do is try to make the footage as least offensive as possible. If the nightshot makes the footage green, remove the green. You might get away with going to a light sepia-tone look. Try playing with the contrast curves to give it a different look. Subtracting the bad is probably all you can do, but you might get away with using some effects that make it look like you did nightshot for a purpose. Perhaps others have done something that may be interesting and will give you an idea.