Aberration A geometrical optics deviation from ideal imaging.
Aspherical Lens A lens that has a curved surface that is neither sphere nor spherical.
Back Focus The distance from the vertex of the final refractive surface of the lens to the image focus.
Chromatic Aberration It is also known as Chromatic Distortion. It is a failure of a lens to focus all colors to one point, usually caused by dispersion.
Comatic Aberration Aberration which mainly occurs with off-axis (comet-like shape) light fluxes.
Depth of Field The distance between the nearest and furthest of an object that is in focus.
Distortion A kind of aberration where an image is not geometrically similar to the input optical image.
Effective Apparatus The diameter of a bundle of parallel rays that enter the lens from a point light source, a point light source assuming to be located at infinite position on the optical axis of the lens.


Field Of View The range of subjects that can be photographed on a certain imaging plane, expressed in degrees of angle.
Fixed Focus Lens A lens with singular field of view.
Flange Back The distance from the flange of the lens to the focal plane. C-mount has a flange back of 17.526mm vs 12.5mm for C-Mount.
Flare A phenomenon when light is scattered in lens creating a bright light of spot in a form of circles, rings, starburst or haze.
Focal Length The distance from the image side of the lens to the image focal point.
F-Stop The F-Stop represents the brightness of the lens. The bigger the value, the darker the F-Stop is.
Ghost Also known as ghosting flare, it is caused by light (scattering and reflection from optical elements and lens barrels) unrelated to image formation.
Imaging Range The range within a distance which subject can be captured.
IRIS It is an element used to control the intensively of illumination being fed in the lens. It is also known as Aperture, and the 4 main types of Iris are, Fixed, Manual, Auto and P-Iris.


Lens Mount Refers to the mechanical connection between the lens and the camera, such as C-mount and CS-mount.
Minimum Object Distance The shortest distance at which a lens can focus.
MTF MTF is the spatial frequency response of an imaging system and is used to evaluate the performance of a lens.
ND Filter Reduces or modifies the intensity of all wavelength or colors of light equally, giving no change in hue of color rendition.


Permissible Circle of Confusion An optical spot caused by a cone of light rays from a lens not coming to a perfect focus when imaging a point source.
Potentiometer A position detector mainly for presetting the zoom, focus, and iris of motorized zoom lenses.
Refractive Index The ratio between the traveling speed of light in medium 1 and the speed of light in medium 2.
Relative Illumination The brightness ratio of the screen periphery to the optical axis of the lens (center of the screen).
Resolution One of the major indicators in lens performance, it indicates how many black/white patterns can be reproduced per 1mm on the film surface.
Spectral Transmittance Transmittance for monochromatic light.
Spherical Aberration Type of Aberration caused by lens element being composed of spherical surfaces. When a ray from one point on the optical axis enters the lens, depending on the distance from the optical axis of the incident point, aberrations differ according to imaging positions.
Spherical Lens A lens that has spherical refractive surfaces on both sides.
Transmittance The ratio of the light intensity transmitted through the lens with incident light intensity.


Vari-Focal Lens A lens with variable focal length in which focus changes as focal length changes.
Zoom Lens A lens which the image size can be varied continuously by moving a part of the optical system along the optical axis, while the image remains in focus.
Zoom Ratio The ratio of the maximum focal length to the minimum focal length.


If you have any questions or concerns, please feel free to contact us.

(C)2022 ADL,Inc.