Apply the Balance
You have to begin by capturing and transferring the footage from the camera so that it is brought into your video editing program. You will often be using an external audio recording device, such as a Zoom recorder, to record audio along with your 5D’s video since it is not capable of high quality sound. Do not worry about that now because you can worry about syncing the sound once you have completed the white balance process. When you are capturing this footage make sure that you are doing so at HDTV 1080p, square pixels, and make sure the capture setting reflect what you had the camera set at.
Once the footage is in your Final Cut Pro Browser, you will want to bring it either into the Timeline to work on instead into the Viewer. Go into the Effects tab and select Video Filters. From here, find the Color folder and inside that choose Color Corrector 3-Way. Drag that filter on the clip, and then make sure the progress bar is on the clip. You will then be able to select the clip, go into the Color Corrector 3-Way tab in the Viewer, and work on it as if you were color grading.
If you want to adjust white balance on the Canon 5D Mark II in Post-processing you will start by going over to the right hand circle, which is the Whites circle. Go to the little arrow box to the lower left hand corner of the circle, and when your cursor lingers over it then it will say “Select Auto-balance Color." When you click it your cursor will become an eye dropper, and you will take that over into the Canvas. This is where the video image should be, as well as the white that has not been properly balanced already. Find the area in your image that you know is intending to be white and click it. This will alter the entire image in accordance with that area being turned correctly white, in the same way that it would when you were white balancing on set.