Choosing a lens for Megapixel Imaging
Why lens selection matters for megapixel applications
When designing or considering the purchase of a Megapixel video system, picking the correct lens is paramount. The lens is the very first step an image takes as it is captured by that system. With Analog and VGA resolution systems, this component of the videosystem was often overlooked. Using any lens off the distributor’s shelf would usually provide an acceptable image by VGA standards because the resolution of the camera was not high enough to require a higher quality lens. This is not the case with Megapixel quality video! The higher the pixel count of the sensor, the more important a high quality lens becomes for optimal image quality. As theresolution and pixel density increase, use of a substandard lens introduces issues such as aliasing and other issues related to modular transfer function.
Why all megapixel lenses are not created equal
Not all lenses marked megapixel are of equal quality because there are no standards for specifying “megapixel”, meaning “megapixel” quality lenses from two manufacturers could vary greatlySpecifications like line pairs per millimeter (lp/mm) which might provide some measure to compare are often not disclosed in the manufactures specifications. The physical pixel size can vary for different imagers as well so a lens rated with a high lp/mm for a 1/2” imager may perform differently on a 1/3” imager.
Image quality delivered by “ megapixel” lenses of the same format, focal length, and F-stopfrom differing manufacturers can vary when applied to the same camera.
Lens A vs. Lens B, quality and image clarity can vary greatly with lenses of equal specifications :
Issue version- 1.1
Application note for
How to go about selecting the right lens?
Get a quality lens One way to be certain of getting a lens that meets the quality megapixel camerasrequire is to get it from Arecont Vision. All lenses that Arecont Vision sells are tested against a number of parameters and only the best are offered. Arecont Vision offers three lens lines that represent different quality and pricing: LENS, MPL, UHD. The LENS line is low cost and good for 1.3 and 2MP. Depending on the application this line could meet the needs of a 3MP or 1080p camera. The MPL lineis very cost competitive and has better quality than the LENS line. MPL lenses can be used on 1.3, 2, 1080p and 3MP cameras as well as could be a good mid-range 5MP lens. The UltraHD or UHD line is the flagship line specifically for the 10MP resolution. For critical 5MP applications, this line is recommended.
Arecont Vision also conducts the same testing against top tier lens manufacturers’“megapixel” lenses. The list of lenses that have successfully passed these tests is supplied at the end of this document. Choose the lens to match the application (Lens specifications & terminology) The angle of view determines the width and height of the image captured by the lens. This is often referred to as the field of view or FOV. The angle of view on a given lens is directly related to the focallength, what size sensor the lens is rated for, i.e. 1/3”, 1/2”, 2/3” and what size sensor is actually used Focal length is the distance between the focus point and the camera sensor and is specified in millimeters, i.e. 10mm. In the camera the image sensor is placed at the focal point of the lens. Some lenses have fixed focal points; others are called vari-focal. Vari-focal 2|Page
Application note for
lenses can be adjusted through a range of focal points and are usually specified and marked with the lowest and highest focal lengths they can be moved between, i.e. 8-16mm. The higher the focal length in millimeters (16mm in this example) the tighter the angle of view and conversely the smaller the focal length (8mm) in millimeters the wider...