![]() ![]() 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. ![]() Your photos will take up more room on your memory card, but you'll be able to print larger and sharper photos. Remember, you can always improve the quality of your photos by putting your camera's MP setting higher. However, if you want to print a larger photo, for example 8-inch-by-10-inch photo, the PPI reduces to 100 for width and 120 for height, giving you lower quality prints. The PPI will be 200, providing you with good quality photos. So, for example, if you want to print a 4-inch-by-6-inch image, and your pixel count is 800 x 1200, you need to divide 800 (the pixel height) by 4 (the photo height) and then divide 1200 (the pixel width) by 6 (the photo width). Calculating PPI The basic equation for calculating PPI is: PPI = width(pixels)/ width of image (inches) PPI = height(pixels)/ height of image (inches).Once you have these two pieces of information (the print size and the pixel count), you can calculate the PPI and determine the resolution of the image. The Properties dialog box that opens will provide you with the details of the photo, including the pixel count. Select Properties from the dropdown menu. To find the pixel count on your photo, open the image on your desktop computer. Then check the pixels of the image you want to print. Size and Pixel Count In order to print a high quality photo, you must first determine the size you want to print.A general rule of thumb is to try to have a PPI of between 200 and 400. The more pixels you have per inch (centimeter), the sharper your photos will be. The pixels on your digital camera or computer screen get converted into dots on the printed photo. What is PPI? The first step to understanding how to print high-quality photos is to understand pixels per inch (PPI). ![]()
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