This LPI number is specific to the printing industry. “Lines” is a throwback reference to the days when actual lines were etched in glass plates to interpret photographic tones in early printing processes. LPI refers to the number of “lines” of halftone dots used by various printing processes. LPI refers to the halftone dot structure used by laser printers and the offset printing process to simulate the continuous tones of photographic images. Internet images are defined by pixel count and concern the linear measurement of horizontal pixels in the image. This particular dialog defines the size of the “Eye” picture in this article. When viewed in imaging software, these squares are referred to as pixels and should be defined in values of pixels per inch (PPI). We’d all be a bit better off not using this term as it has little practical application. DPI, or dots per inch, is a reference to printing device’s resolution and describes the dots and spots that each technology uses in various combinations to simulate “tones.” Dots are neither pixels nor halftone dots. The term DPI is probably the most misconstrued acronym in the digital imaging world as it is loosely cast about in digital imaging and applied to just about every device. Allow me to clarify some very foggy air beginning with terminology. There is ample misinformation and misused terminology floating around that causes significant confusion about imaging resolution. Dots, Pixels, Lines, and Spotsīeware of the numbers game that is played by manufacturers in the imaging industry. While you feel more confident when you pass massive amounts of pixels on to your printer, your printer doesn’t appreciate the excess. Producing more image resolution than the eye can perceive doesn’t increase the detail or improve the definition, it just creates bigger files. Thus, the gauge of all visual resolution must ultimately be framed by resolving capabilities of the human eye. In the image reproduction process, delivering an image with excess resolution becomes useless when the result of that extra resolution has no purpose. There are limitations to the normal resolving power of the human eye with “normal” defined as 20-20 vision. The detail you see when viewing an object at close range continues to be perceived long after that object is too far away to verify that detail. Beyond that point, your brain must sell the idea that detail indeed exists beyond that point of distinction. There comes a finite distance when viewing any image where your eye can no longer distinguish individual colors. Now let’s get image resolution explained and show you where it’s is most effectively used. The common phrases, “seeing is believing,” and “perception is reality,” pretty much define the benchmark of success. Just as a magic trick requires both a salesman (the magician) and a customer (the viewer), each “visual” process requires a good presenter and a willing observer. The degree to which each device succeeds in their illusionary quest is dependent upon the resolution of the mechanism and the resolving power of the device.Įach system requires two elements – a transmitter and a receiver. The eye’s mechanism is rods and cones, cameras use photo receptors, computer screens use pixels, and printing machines use spots and halftone dots. Each of these “interpretations” relies on a mechanism to carry out an illusion. This same issue is true concerning the human eye and its perception of images on a computer screen and the printed page. The resolving power of a lens is its ability to distinguish small elements of detail. The very word “resolution” gives light to this concept. Your brain chooses to believe something to be true well beyond what your eyes can verify or recognize to be true. This concept didn’t originate with photography’s pixels and dots it is the very basis for human sight. The very first thing you must understand about photography is that it is totally based on illusion you choose to believe what you perceive.
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