Focal Length:          fc = [ 854.97854   827.06613 ] ? [ 57.04005   44.54214 ]
Principal point:       cc = [ 577.05718   144.98053 ] ? [ 65.87774   31.91019 ]
Skew:             alpha_c = [ 0.00000 ] ? [ 0.00000  ]   => angle of pixel axes = 90.00000 ? 0.00000 degrees
Distortion:    schwer        kc = [ 0.00695   0.08362   -0.02177   0.07246  0.00000 ] ? [ 0.09210   0.06453   0.01507   0.02623  0.00000 ]
Pixel error:          err = [ 2.96180   2.16437 ]

? =  +-

initialisation without uncertancies
Focal Length:          fc = [ 333.06491   333.06491 ]
Principal point:       cc = [ 319.50000   239.50000 ]
Skew:             alpha_c = [ 0.00000 ]   => angle of pixel = 90.00000 degrees
Distortion:            kc = [ 0.00000   0.00000   0.00000   0.00000   0.00000 ]

The pixel errors are mean re-projection error for extracted grid points, i.e. the actual pixel location and the one by using calculated K matrix.
Initialization of the principal point at the center of the image.

removing picture 11,2,4,3

Calibration results after optimization (with uncertainties):

Focal Length:          fc = [ 802.16252   784.80772 ] ? [ 35.88106   32.30823 ]
Principal point:       cc = [ 409.60542   137.13751 ] ? [ 36.82844   42.37479 ]
Skew:             alpha_c = [ 0.00000 ] ? [ 0.00000  ]   => angle of pixel axes = 90.00000 ? 0.00000 degrees
Distortion:            kc = [ -0.14710   0.14740   -0.01636   0.00052  0.00000 ] ? [ 0.06378   0.16835   0.01201   0.01046  0.00000 ]
Pixel error:          err = [ 1.33896   1.25581 ]

Note: The numerical errors are approximately three times the standard deviations (for reference).