Distortion

No camera lens is perfect. Through testing, it has been found that the most precise while still simple model of distortion introduced by a camera lens in general involves two parameters describing the radial distortion; tangenetial distortion is generally ignored. The two terms are defined by the equation

$\tilde{x} = x \{1 + [k_1(x^2 + y^2) + k_2(x^2 + y^2)^2]\}$

. $k_1$ is the stronger parameter. $\tilde{x}$ is a distorted point in an image (as captured by the camera), while x is the real point in the image plane. Later, x and y stand for individual coordinates in the point.