A-E
| 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. |
F-J
| 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. |
K-O
| Lens Mount | Refers to the mechanical connection between the lens and the camera, such as C-mount and CS-mount. |
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| 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. |
P-T
| 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. |
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| 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. |
U-Z
| 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. |
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