Hikvision Announces ColorVu 2.0 Camera-4K and Varifocal Options
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Delivering better video quality and rich detail, 4K ColorVu cameras can be used more widely in situations such as stadiums, airports, harbors, and parking lots where clear, high-resolution video is required.
Hikvision ColorVu 2.0 Camera AsiaNet 86136 (1870) [Hangzhou (China… → Continue reading
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The unit is generally dot per inch (dpi).Pixel per inch (similar concept)ppi), Line per inch (lpi), The former isScan lineIn the performance notation of scanners, etc., the latter two are mainly used for objects that are printed or displayed as a surface by a set of fine lines.See each item for each unit.It is not possible to compare these values directly.Other than these units, you won't see them in general, but the pixels per meter (ppm) Exists.This is,Bitmap image,PNGIt is used inside the image format such as.Most image display software converts ppm units to ppi units and displays them, so it is rare to see them.
Original resolution (physical resolution)
The original resolution means how detailed the observation target is measured (depicted), or in other words, how far different objects are separated. dpi is a unit that expresses the density of dots, which is a well-defined physical quantity, and the use of the term resolution, which has a meaning as a relative density depending on the size of the screen, is not the original usage.The problem will be clarified by taking the above figure "difference in resolution" as an example.
At first glance, this figure "difference in resolution" is clear, and the figure on the far right has the highest physical resolution.However, we are seeing the same dpi display on the screen, depending on the size of the screen (relative).Number of pixelsHas a different meaning than (physical) resolution.This figure,Analog silver halide photography(To the right)FocusIs correct)Image scannerYou can think of it as a bitmap image captured at the same dpi.No matter how high dpi the image other than the right edge isMonitor display,PrintEven so, the resolution will not be higher than the right end (physical).
Such confusion is due to the use of "resolution" for the physical resolution and the relative resolution that is related to the size of the image.However, the physical resolution is dpi, and the relative resolution, which is related to the size of the image,PixelA unit that indicates the number and the physical size of the screen (inch) Is used.
FormerComputer displayShifted from an impact printer to a display using a CRT (Cathode Ray Tube), and due to technical restrictions on the CRT, the resolution of the central part of the screen was lower than that of the left and right edges of the screen.In the era when non-uniform display resolutions were the mainstream, character string display (character display) was the mainstream, so the difference in physical resolution was not an issue.Also, for graphic displays that require uniformity,Vector scanA special type of device was used.afterwards,Graphical user interfaceThe CRT was required to have a dot display performance with squares in the vertical and horizontal directions.For consumer displays, Apple MacintoshGraphical user interfaceWith a setting that leads the CRT with a performance of about 80-100dpi and has a margin, "1PointWe decided to assign "= 1 dot" to express a 72dpi square dot.Even now, display displays are often made based on square displays.However, in the final stages of CRT, performance improved and computer displays came to have a resolution of 100-150 dpi. Microsoft Windows was set on the premise of 96dpi performance.In recent years, since liquid crystal displays have become mainstream, it has become possible to obtain a uniform resolution on the screen, and therefore, high resolution has been attracting attention again.OSX,iOSIn OS such as, the point unit (logical unit) is used instead of the dot unit (physical unit) to control the GUI (the GUI can be physically the same size on any display).For this reason, characters of the same size may become clear or rough due to the difference in display dpi.Similarly, in android and windows 8 or later, logical dot units are set.
Printed matter (Image resolution)
Printed matterAlthough the resolution depends on the printing method, it often has a resolution of about 300 to 600 dpi for general household use and 600 dpi to 2400 dpi for commercial printed matter.However, in a printer, the resolution represents the amount of deviation of the center of dots, so even if printing is performed at that resolution, it is not always possible to see the separated individual dots.
The resolution is originally to display or print an image.deviceIt is a parameter determined by the characteristics of.Therefore, the resolution information added to the image data itself is only auxiliary information such as "I want you to display at this resolution" or "If you display at this resolution, it will be the actual size".
Communication and broadcasting
In many cases, the horizontal resolution and the vertical resolution are the same, so the resolution is indicated by a single numerical value, but in the case of image data for printing and image data for communication, the resolution is higher in the horizontal and vertical directions. It can be different.That is, the intended image shape is obtained by displaying the width and length of one pixel in different states.The ratio of horizontal and vertical resolution at this time is "Pixel aspect ratio(pixel aspect ratio) ”.
Widely used in the broadcasting fieldYUV formatThen, the color of each pixel is indicated by three parameters of luminance information Y, color difference information Cr, and Cb, but in order to reduce the amount of data in communication, the color difference information is often set to half the resolution of the luminance information. It has been.
Also, how many different colors can be held for each point?Color depth,Color resolutionorColor resolutionCalled.Color resolution is often indicated by the number of steps in which the intensity of each of the three primary colors of light, "red, green, and blue," can be expressed.Also, this number of stages is 2.LogarithmIs often expressed as the number of bits using.For example, a bitmap image called 24-bit true color, which is widely used as data with high color resolution, has 256 levels of color resolution for each color.This is expressed as a color resolution of 8 bits for each color, for a total of 24 bits.
HumanEye TheLight Ofthree primary colorsOf these, it is known that the sensitivity to blue is weak.Therefore, even if the color resolution of blue is lower than that of red and green, the effect on image quality is small.From this, the color is expressed by a total of 6 bits, 4 bits each for red and green and 16 bits for blue, and the color is expressed with a total of 3 bits, 2 bits each for red and green and 8 bits for blue. Is often done.These color representations are sometimes called 16-bit true color or 8-bit true color.In addition, the one in which 5 bits are assigned to red and blue and 6 bits are assigned to green, and the one in which 5 bits are assigned to red, green, and blue are called high color.
It is generally said that the human eye has the ability to distinguish about 1000 million colors.With 24-bit color resolution, 224= 16,777,216 colors can be expressed, which exceeds the characteristics of the human eye.However, as mentioned above, the color resolution of the human eye differs depending on the color, and there is a research result that red is not enough if there are about 10 bits.For this reason, when emphasizing color reproducibility such as image creation for movies, data having a color resolution of 10 bits, in which 30 bits are assigned to each of red, green, and blue, may be used.
The resolution is originally as described abovePixel densityAlthough it is a value indicating, it is also used as a term indicating the number of pixels of an image.This is the TVHorizontal resolutionThis is because it is derived from the concept of.Screen resolutionSee.
- What is resolution? --Video terminology Webliodictionary
- What is resolution (kaizoudo)? - Koto bank
- What is optical resolution? -Kotobank
- What is Interpolation Resolution (Other Kaizoudo)? -Kotobank
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