Method for spectral calibration of a color image sensor for images of HxW pixels and comprising HxW photosites, wherein it comprises the steps of: a) for each sensor photosite of row i and column j, obtaining a spectral calibration function f i,j (λ) giving an intensity for the signal from the photosite i,j as a function of the light wavelength for the photosite, b) from at least one standard image of dimensions HxW and of known light intensity levels at each pixel for at least K colors, constructing a first matrix system X comprising: - for each row, n.m matrix elements respectively corresponding to intensities of pixels in the neighborhood of a central pixel of the standard image, said intensities each being modulated by a corresponding calibration function f i,j (λ) for row i and column j of a pixel of the standard image, - for W.H rows, c) for said standard image, constructing a second matrix system Y comprising: - in each row, the K actual signal intensity levels for said K colors, for each pixel of the standard image, - for W.H rows, d) and establishing a calibration matrix system H for the transformation between the first matrix system X and the second matrix system Y, such that H.X = Y, the calibration matrix system H representing said spatial-chromatic transfer function, in order to obtain, from a first current matrix system X' constructed by applying step b) to a current image captured by the sensor, an actual distribution of color intensity levels according to a second current matrix system Y' for each pixel of this current image, and such that H.X' = Y'. a) for each sensor photosite of row i and column j, obtaining a spectral calibration function f i,j (λ) giving an intensity for the signal from the photosite i,j as a function of the light wavelength for the photosite, b) from at least one standard image of dimensions HxW and of known light intensity levels at each pixel for at least K colors, constructing a first matrix system X comprising: - for each row, n.m matrix elements respectively corresponding to intensities of pixels in the neighborhood of a central pixel of the standard image, said intensities each being modulated by a corresponding calibration function f i,j (λ) for row i and column j of a pixel of the standard image, - for W.H rows, - for each row, n.m matrix elements respectively corresponding to intensities of pixels in the neighborhood of a central pixel of the standard image, said intensities each being modulated by a corresponding calibration function f i,j (λ) for row i and column j of a pixel of the standard image, - for W.H rows, c) for said standard image, constructing a second matrix system Y comprising: - in each row, the K actual signal intensity levels for said K colors, for each pixel of the standard image, - for W.H rows, - in each row, the K actual signal intensity levels for said K colors, for each pixel of the standard image, - for W.H rows, d) and establishing a calibration matrix system H for the transformation between the first matrix system X and the second matrix system Y, such that H.X = Y, the calibration matrix system H representing said spatial-chromatic transfer function, in order to obtain, from a first current matrix system X' constructed by applying step b) to a current image captured by the sensor, an actual distribution of color intensity levels according to a second current matrix system Y' for each pixel of this current image, and such that H.X' = Y'.