20mm F1.4 DG HSM | A Refurbished

10 lines per millimeter measure the lens?s contrast ability ( red lines), repeating fine parallel lines spaced at 30 lines per millimeter measure the lens?s sharpness ability (green lines), when the aperture is wide open.

Diffraction MTF takes diffracted light at every aperture into account which is very close to actual image data. Geometrical MTF does not consider the diffraction quality of light, yet it tends to show higher values than actual image.

Diffraction MTF takes diffracted light at every aperture into account which is very close to actual image data. Geometrical MTF does not consider the diffraction quality of light, yet it tends to show higher values than actual image.

Vignetting

The horizontal axis shows the image height (the distance from the center to the edge of the image [mm]). The vertical axis shows the amount of light in the image (based on the amount of light in the image center being 100%)

Relative Distortion The image will be seen as expanded (barrel distortion) in negative values or will be seen as a recessed (pincushion distortion) in positive distortion values.