![]() ![]() The average FOV width for the human eye is 140 degrees. This is the Shortest Recommended Viewing Distance based on Field-of-View being too wide: This distance is calculated on the peripheral vision field of view of the human eye. The audience should sit at least this distance from the screen.The wider the field of view, the more noticeable the effect. This rectilinearity creates an effect called 3D stretching or lean-over, in which objects at the edges seem to be stretched (Figure 2). With a rectilinear lens, objects in a common plane perpendicular to the camera have the same image resolution at the center and edge, even though the objects at the edges are farther away from the camera. With a rectilinear lens, the image is spread over a greater number of pixels at the edges, increasing the probability of identification. Any dewarping will create an image that looks like that from a rectilinear lens but at lower resolution. With typical distorted wide-angle lenses, potentially valuable information is lost, and no software can reconstruct the lost information. ![]() This increases the resolution at the edges lenses with barrel distortion lead to compressed edges and reduced resolution. Rectilinear lenses keep lines that appear straight in the real world straight on the image sensor. With a view greater than 90 degrees, most wide-angle lenses will have barrel distortion (also known as fisheye distortion) where image look curved and bulged out in the center. The shorter the lens' focal length, the wider the field of view. Clearly, the higher the number of pixels, the wider the field of view it acquires at a constant image resolution. As the camera resolution (total number of pixels) increases, so does the field of view (pixels per foot). As available pixels across the field of view are greater, the field of view can be increased without decreasing image resolution.įigure 1 compares the field of view of different cameras at a distance of 32 feet from the subject at the same image resolution. Wide angle field of viewĪn advantage of megapixel cameras is the ability to cover a much wider area with the same or better resolution compared to its analog counterparts. The rest of the article takes on this definition. ![]() This gives the number of pixels per foot that can be correlated to image quality. It is basically the horizontal field of view (HFOV) of the camera divided by the horizontal number of pixels. Last, resolution can be specified in pixels per foot or meter at an object. As the total number of pixels on an image sensor increases, the pixel size gets smaller and requires a lens of higher quality to achieve focus. Commonly used by lens designers and optical engineers, image sensor resolution is expressed as line pairs per millimeter (lpm). Resolution can also be the level of detail with which an image can be reproduced or recorded. With megapixel cameras, resolution is generally expressed with the total number of pixels, divided by one million and rounded off. Resolution can be expressed with the number of pixels of the image sensor. Read More: The tradeoff between field of view and resolution Read More: How to differentiate between quality megapixel lenses There is a balance that must be made between level of detail and project budget. It must be said, however, that 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 note looks into how image resolution can be calculated. That’s why calculating image resolution is a good knowledge to have. The detail in an image is determined by resolution. ![]()
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