![]() In order to calculate the appropriate lens value for a given sensor resolution and size to meet pixel density requirements is commonly done with design software, due to the vast number of possibilities available in the market today.īy utilizing software such as our design tool, the system designer can quickly determine the appropriate sensor, lens, and camera position to achieve the desired level of detail for a given camera location. Pixel density calculations do not take into account sensor size, or lens parameters, they are a factor of the resolution of the sensor, and the width of the scene. If we use the same camera to cover an area 60M/200FT wide, we would have 32PPM / 2PPF, which would only enable us to know that there is general activity in the area, but we would not be able to see specific details about the scene or objects. If we take an area of the image that is approximately 6 meters, or 20 feet, wide we would calculate: 1920px / 6M = 320 PPM, oe 1920px / 20FT = 96 PPF, which would yield a very high detail image, assuming sufficient lighting, focus, etc. Pixel Density CalculationsĪs an example, let’s take a common 1080p camera sensor, which is 1920 pixels wide, and 1080 pixels tall. Still, without calculating appropriate detail levels for the common scenario we have no hope of delivering a system that meets customer needs. It is important to note that final image quality is dependent on a number of factors, including available lighting, camera focus, shutter speed, codec compression, and other criteria. With higher pixel density, you can distinguish smaller details. The higher the pixel density, the higher the quality of the picture. ![]() Image detail quantified in pixels per meter or pixels per foot (PPM/PPF numbers based on mm per pixel specified by IEC/European Standard EN 62676-4: 2015) ![]() The following image shows representative examples of each level:įigure 1. Pixel density is obtained by dividing the camera horizontal resolution by field of view width.ĬCTV system designers tend to use the following categories to describe pixel density levels in an image, in order from most to least detailed: The image below depicts varying degrees of pixelization. A better method of defining image detail is by pixel density on a target (pixels per foot or pixels per meter). One of the constraints of extracting image detail from a live or recorded video image is that the user is limited by the fact that any detail must be present in the original image. You may also come across PPI (pixels per inch) or PPCM (pixels per centimeter) when dealing with specifications for monitors or printers, where the area of the pixels, such as a piece of paper, is much smaller than the area viewed by a typical CCTV camera. These terms refer to how many pixels of an image sensor would be spread across a 1 meter or 1 foot horizontal measurement in a scene. Specific pixel density levels in CCTV images are referred to as PPM (pixels per meter) or PPF (pixels per foot), depending on the region where the system is being specified. It does not address how many of those pixels are focused on a specific object or area of the image, which is the pixel density. Resolution describes the total number of pixels in an image, or the total number of pixels of an image sensor. Sometimes resolution is confused with pixel density, particularly by users not familiar with CCTV concepts. Calculating which sensor and lens combination is required to deliver the right level of detail, or pixel density, in a given area is the job of the qualified system designer. That same sensor mounted high above a large parking lot, looking at an area large enough to hold 500 vehicles would capture very little detail. As you might imagine, a 4MP (mega-pixel) image sensor looking at an area the size of a postage stamp would capture very high detail. In order for our systems to meet the expectations of the users we need to first know what level of detail the user requires, often referred to as “Pixel Density”. These factors can lead some users to expect more detail from their CCTV systems than the system is actually capable of. Our cellphones can capture images at 10 megapixels or more, common televisions can stream 4K content, and multi-megapixel CCTV cameras are part of almost every system installed today. We are surrounded by high detail images every day.
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