Questions and Answers, Technical Information
DeFog zoom lens features sophisticated IR pass optical filter to block the visible light and transmit only near-infrared light with the ability to provide crystal clear images even under adverse atmospheric conditions, such as fog, haze, dust, mist, rain or snowfall.
Although atmospheric particles scatter most of visible light with a shorter wavelength, near-infrared light passes through atmosphere and a fairly large portion of these rays reach the objective even under the adverse atmospheric conditions.
Standard lenses are made from a combination of spherical lens elements. However, there can be problems with such lenses when light entering at the edges of the lens may not be perfectly focused at the same point as light entering at the center. That presents limits to performance in wide aperture and super wide-angle lenses. Tokina uses aspherical glass elements in many lenses. In addition to correcting spherical aberration, these lenses fully correct light quantity and image distortion and provide excellent results when used in combination with floating elements. Through technical cooperation with Hoya, KenkoTokina has succeeded in producing high quality molded glass elements with a greater aspherical shape than any other lens so far. This technique is unparalleled in its technological sophistication and excellence.
Lenses with the SD mark use Super-low Dispersion glass which minimizes the secondary spectrum caused by chromatic aberration. Basically, these lenses use FK01 and FK02 optical materials which give them SD (APO) quality. This provides excellent image quality in telephoto lenses of 200mm or more.
The F-number is an index of the amount of light that passes through a lens. The smaller the number is, the greater the amount of light is. The relationship during F-number, focal length and effective diameter can be calculated by the following formula.
F-number=f/A f=focal length A=effective diameter
CCTV lenses are usually used on C-mount or CS-mount. Both have same shape but with different flange focal length. C-mount has 17.526mm and CS-mount has 12.5mm as flange focal length.
Back focal length … The distance between the last lens element of the lens group and focal point.
Flange focal length … The distance between flange surface (the contact surface of camera and lens) and focal point.
The closest distance which a lens can focus on an object. Generally the smaller the focal length is, the shorter the M.O.D. is. This distance can be altered with use of extension tubes.
Focal length is the distance from the 2nd principal point to focal point. With short focal length the field of view will be larger. With long focal length, the field of view will be narrow.
This function allows a lens to feedback information regarding zoom and focus position to the controller when used with an appropriate controller. The controller will quickly scan a preselected scene and adjust focusing on the proper point without operator intervention.
■ General Info
Since conventional CCTV lenses are being designed for the visible spectrum, using in the (near) infrared, image will appear blurry even after re-adjusting focus. The TOKINA IR lens provides no focus shift between visible and near infrared light. Besides, it produces a clear image because it has extremely fine resolution in near infrared light. That is why Tokina has developed totally new Infrared Corrected (IR) Lens, a CCTV lens perfect to work with Day/Night or High Sensitivity HAD cameras.
Using a surveillance system that combines the Tokina IR lenses with Day/Night Cameras eliminates re-adjustment of the focus position.
Once focused, the image will remain perfectly sharp. Day, Night or IR 24/7 in focus.
■ Near Infrared Lens Resolution
Recent technological progress in CCTV cameras produces “Day/Night or High Sensitivity HAD Cameras”. This makes it possible to offer day time monitoring in color and night time monitoring in black and white. It also allows monitoring in total darkness when using infrared illumination. However, conventional CCTV lenses cannot focus completely in the infrared area.
Auto iris is driven, allowing it to adjust the iris automatically opening to incessant change in the amount of light throughout the day. There are two types of auto iris lenses: Video iris and DC iris.
■ 1. Video Iris
Video iris type of lens features not only drive unit (galvanometer or DC motor) but also iris amplifier to control iris and adjust its level by receiving video analog signal from the camera. (Auto iris mode on the camera must be set to ”Video iris”.)
■ 1-2. Manual override
Even during operation of video iris, the specified inputting voltage at appointed wires on the driving cable ensures the arbitrary controlling of
■ 2. DC Iris
DC iris type of lens does not have iris amplifier. The direct connection of drive unit (galvanometer) of the lens and the camera with built-in iris amplifier, the direct iris control becomes possible. (Auto iris mode on the camera must be set to ”DC iris” and iris level must be adjusted on
CCTV Zoom lens are not designed to be controlled by pulse-width modulation (PWM). For further information please don’t hesitate to contact us.
Each Kenko Tokina lens is manufactured under precise standards and has been subjected to stringent quality control inspections throughout the whole manufacturing process. It is warranted to be free from defects in material and workmanship for a period of one (1) year from date of purchase.
This warranty does not cover repair issues related, but not limited to:
Damage caused by misuse, accident, or careless handling
Damage caused by water, mold, or other foreign substance(s)
Damage caused by tampering, repair, or attempt to repair, by any unauthorized repair service or individual
Damage caused by modification