You will be ok.
They will fine the other cars though, you cant fool a gatso.
The reason it takes 2 pictures is to prove youre speed.
How it works:
The radar sensors detects speeding car...and triggers camera.
Camera takes 2 snaps which are a set time appart. (i.e. .5 second)
The distance traveled by ALL cars in the picture is shown by the white markings on the road. Lets assume the markings are 1 appart.
The time is known and the distance, so the speed is easily calculated for everything in the pictures.
If your car traveled over 2 markings in 0.5 seconds
2 x 0.5s = 1 foot per second.
distance x time = speed