Resolution
The resolving power of an optical system refers to the distinguishability of two smallest structures that can still be perceived separately. The resolution of optical devices is limited by diffraction. The typical specification is made in line pairs per mm (Lp/mm). The dependence of the resolution on the contrast describes the modulation transfer function.
Modulation transfer function (MTF)
The MTF, also called contrast transfer function, describes the comparison of the contrast of the edges of a (real) object with the contrast of its image at a resolution (MTF = image contrast/object contrast). A loss of contrast is always obtained.
Contrast
Contrast describes the ratio between light and dark areas of an image, given as a percentage (%).
Depth of field
Depth of Field (DOF) describes the extent of the sharp area (in object space), in front of and behind the optimal focal plane. The smaller the aperture (i.e., the larger the f-number), the greater the depth of field. A special case is the hyperfocal distance, where the depth of field range extends backward to infinity. With telecentric lenses, the telecentric range is essentially the depth of field range.
Distortion
Distortion, or optical distortion, is a geometric aberration of lens systems. It leads to different magnifications at increasing distance from the optical axis of the system and causes the image of straight lines that do not pass through the center of the image to be rendered curved. With decreasing magnification (reduction) to the edge of the image field, one speaks of barrel distortion (fisheye effect) and with increasing magnification of pincushion distortion. Distortion is usually expressed as a percentage (%).