This increase in field of view is also shown in Figure 1 below.įigure 1: Field of view increases with increasing camera resolution (total number of pixels) without any change in image resolution (pixels per foot). Clearly the higher the number of pixels in the camera, the wider the field of view at a constant image resolution. As the camera resolution (total number of pixels) increases, so does the field of view at constant image resolution (pixels per foot). Table 3 below compares the field of view of different cameras at 32 feet from the subject at the same image resolution. Because the total available pixels spread across the field of view is greater, the field of view can be increased without decreasing image resolution. Wide angle field of viewĪ higher resolution megapixel camera (5MP) can cover a larger field of view at the same image resolution as a lower resolution megapixel camera (1.3MP). Table 2: As field of view increases the pixels per foot decreases so that each picture has the same number of pixels and thus causes the same amount of network loading. Because there are no more pixels in one image compared to another, there is no effect on the amount of data transferred over the network and no degradation of network performance by going to either higher image resolution or greater field of view. Each image has the same number of pixels but as the field of view increases, the pixels per foot in the image decreases. In Table 2 below, an image is shown at different levels of resolution from “high detail” for clear identification at 60pix/ft to “motion tracking” for wide field of view at 10pix/ft. There is a balance that must be made between level of detail and project budget. However, higher detail requires higher resolution cameras or more cameras and thus more bandwidth and storage. For security applications, the more pixels on a target, the higher the resolution will be, and the more likely recognition and positive identification will be made. There is not yet an industry standard for the level of sharpness required in every video surveillance application (detection or identification) or machine vision application (barcode or license plate reading). This is the definition that I will expand upon further in the rest of this white paper. This gives a pixels per foot number that can be related to image quality. Fundamentally it is the horizontal field of view (HFOV) of the camera divided by the horizontal number of pixels. This mapping of the image sensor dimensions onto the object is most intuitive for calculating what level of detail can be seen in the image. These high-quality lenses, including those manufactured by Theia Technologies, are rated for megapixel or multi megapixel cameras meaning the image will be sharply in focus at the camera resolution it is rated for.ĭefinition 4: Resolution can be specified in pixels per foot or meter at the object. As the total number of pixels on an image sensor increases, the pixel size gets smaller and requires a higher quality lens to achieve best focus. At the image sensor resolution is expressed as line pairs per millimeter (lpm) commonly used by lens designers and optical engineers. Table 1 below shows examples of typical megapixel camera resolutions.ĭefinition 3: Resolution can be the level of detail with which an image can be reproduced or recorded. With megapixel cameras, the resolution is generally the total number of pixels, divided by 1,000,000, and rounded off. Unfortunately, there is no uniformity in this definition so numbers like 720 or 1080 refer to the number of pixel rows (vertical) but 4k (~4000 pixels) refers to the pixel columns (horizontal) of the sensor.ĭefinition 2: Resolution can be expressed as the total number of pixels. The greater the number of lines, the greater detail or larger field of view can be recorded with the camera. Here we list only the definitions relevant to video in surveillance and machine vision applications.ĭefinition 1: Resolution can be expressed as the number of pixel rows or columns on the sensor used to record an image. Resolution has many definitions no one definition is correct for all situations. Rectilinear lenses such as those using Theia Technologies’ Linear Optical Technology® do not exhibit barrel distortion and thus maintain image resolution out to the edge of the image. Greater than about 90° most lenses start to show curved, barrel distorted images that compress the image at the edges. The shorter the lens focal length, the wider the field of view. The detail in an image is determined by resolution. Mark Peterson, VP Advanced Technology, Theia Technologies
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