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Auto-Iris Vari-Focal Lenses
Data Sheet PDF
A new optical design uses glass mould aspherical lens elements and a special optical coating that ensures 3MP high resolution even under IR light. The addition of a P-Iris model to this series allows an even more precise adjustment of the Iris to gain the optimal depth of field and light exposure.
Focus Shift is the condition that occurs when images that are sharp and in focus under artificial lighting (such as external cameras illuminated with IR lighting at night) are out of focus (appear soft or blurred) in daylight conditions and vice versa. The problem is caused by the nature of light. Different types of light have different wavelengths which means that an image viewed in different light conditions will appear slightly differently. Unless the lens is adjusted for different light conditions, it is impossible for a standard lens to produce a sharply focused image in all types of light. To overcome this lenses either have to be adjusted manually for day and night time performance (impractical) or, if the camera is fitted with a remote controlled motor zoom lens, the picture may easily be brought back into focus (not possible with static lenses, of course, or on an unmanned site). This is why Ernitec recommends fitting IR corrected lenses.
By using variable focal length lenses, stock levels can be reduced and the installation is simplified.
This range includes manual iris and direct drive iris lenses. The direct drive lenses are based on a galvanometric iris.
IR-corrected lenses should always be used and not only when using IR-illumination at night time. Many light sources include a part of IR-light, small or light. In connection with monochrome- or day/night cameras IR-corrected lenses will provide a sharper picture because all the light is focused, resulting in a far crisper picture compared to ordinary lenses. Sunlight contains much IR-light, but also many artificial light sources, especially halogen. Also, ordinary incandescent light bulbs include a considerable amount of IR-light. When having illumination with a mixture of visible and infrared light, it is possible to obtain a considerable improvement of the picture reproduction without having to replace the camera - just by replacing the lens. So there are excellent reasons for using IR corrected lenses in all environments.