As far as I know (somewhat approximate because pneumatic pressure isn't the only thing holding the car up, the tire's also a spring being deformed and resists) you can't change the size of the contact patch with camber, only the shape. With a certain PSI, your contact patch is just the load on that tire divided by square inches. Eg. at 25psi and 500lb load that tire would have 20 square inches of contact patch.
If you're at 0 camber it's a horizontal line across the wheel, if you're at camber then it turns into a sorta triangle shape larger on the edge of the tire hitting the road.