1. Method for forming a model for improving image quality of a digital image captured with an imaging module comprising at least an imaging optics and an image sensor, where the digital image is formed through the imaging optics onto a light sensitive image sensor, the method comprising: determining a vignetting effect of the digital image captured with the imaging module for at least two of plural primary color pixels of the light sensitive image sensor, formulating vignetting models for said at least two primary color pixels of said light sensitive image sensor, and combining said vignetting models into a single correction function defined using correction coefficients, the correction function defining a correction gain for different points (x,y) of the digital image wherein a corrected value for a certain point (x,y) is determine by multiplying an original value of the certain point (x,y) by the correction gain on the same point (x,y), and the corrected value is formulated mathematically as follows: 
 C CORRECTED ( x,y )= C ORIGINAL ( x,y )GAIN VE ( x,y ), where the correction gain is formulated mathematically as follows: 
 GAIN VE ( X,Y )=1.0+ C COEFF ·a COEFF ·( a 1 ·d ( x,y ) 2 +a 2 ·d ( x,y ) 4 +a 3 ·d ( x,y ) 6 ), where distance parameters d(x,y) 2 describe distance from a center of vignetting to the certain point (x,y), parameters a 1 , a 2 , a 3 , describe correction coefficients for a certain optic-sensor-module, coefficient a COEFF determines a degree of compensation, and color-specific coefficient C COEFF , which describes behavior of a certain color, is determined for each primary color pixel separately.