Of course some of the most impressive CG work is that which is integrated into live footage. After working with this for years, I finally come down to a method that will help you achieve realistic results. For $1.30 my life has been made easier.
Buy yourself a foam ball for reference lighting. Here’s 2 images thanks to this method of working.
The third is an image of a CG AK-47 using reference lighting.
Size reference also. For instance, I know the ball is 3" in diameter. So if I’m filming in a large area, I can use it to help me measure size and length.
This technique was shown in Jeremy Birn’s Book Digital Lighting and Rendering. You could use the ball for size reference but the real purpose is for lighting the scene.
For example, if you photograph the ball the picture can assist you when you assign a color to your spotlights for lighting the 3d object. When assigning the color just click the eye dropper tool and (with the photo of the ball in the UV image editor) select the area of the ball that corresponds to the direction that your light is pointing.
I’ve never tried this but if you use this technique then your colors will be very accurate. This isn’t explained in Jeremy Birn’s book but I think for best results you should place the ball in the same spot that the CG object will go.