IPS vs. LPS Screen

IPS ((In-Plane Switching technology): was originally developed by Hitachi and had been in use from the mind nineties. Earlier to this twisted nematic (TN) technology was used to make panels for monitors. Hitachi introduced the IPS technology for liquid crystal display (LCD) panels. This technology was used to overcome limitations faced by TN matrices, which included slow response, small viewing angles and low quality colour reproduction. The new technology of In-Plane Switching (IPS) introduced arrangement and switching of the molecules of the liquid crystal (LC) layer between the glass substrates in a plane parallel to these glass plates. This technology made a lot improvement in the colours schemes and the resolution in the technology used in twisted nematic (TN) monitors. It provided a better viewing angles and better resistance to touching. Hitachi went on making improvements in this technology making the IPS displays quite popular among the users. 

In 2010, Samsung emerged as Hitachi's main competitor by introducing yet another new technology called PLS (Plane-to-Line Switching). The intention of Samsung was quite clear. It wanted to supersede and overtake the conventional IPS technology introduced by Hitachi in the mid nineties. PLS technology introduced by Samsung became the company's wide-viewing angle technology. Samsung has claimed that the PLS technology has further improved the viewing angle. It claims to have increased 10 percent increase in brightness. The company also boasts of 15 per cent decrease in the production costs. There is increase in image quality and in the flexibility of the panel.

Both the IPS and PLS technologies are almost similar, and it is very difficult for the common user to know as to which technology has been used in the display screens. However, the PLS screens are known to be brighter and have better viewing angles. The PLS panels do not change colour on touching them. They do not leave a trail when the user drags his or her finger across the panel. The difference in both the panels is more of a technical and practical value. They are very small and mostly insignificant in the real life situations.

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CONVENTIONAL PRINTING vs. STOCHASTIC PRINTING

Advantages of stochastic printing versus conventional printing:

• Continuous tone photographic reproduction
• Produces a larger CMYK color gamut on press
• Renders greater detail
• Eliminates moire patterns
• Reduces ink consumption by as much as 10% – notice the ‘pooling’ of ink in conventional dot
• Produces smoother gradients
• More consistency in color throughout pressrun
• Faster ink drying

Conventional screening (150 lpi, 175 lpi, 200 lpi) refers to AM screens, or amplitude modulation. This refers to halftone dots that are fixed on a grid, angled in 30 degree increments (except yellow: 15 degrees) and grow in size based on tonal value.

LPI = lines per inch

Stochastic screening (Staccato) refers to FM screens, or frequency modulation. This refers to micro-dots (20 micron, 10 micron) that are FIXED in size and tone values increase by adding more dots. The dots are rendered in a psuedo-random algorithm making them ideal for high definition details in photography and artwork. The micro-dots are rendered in a ‘weave’ to create very smooth tonal transitions.

Micron =1/1,000,000 of a meter

It’s important to note that stochastic printing produces a larger CMYK color gamut than AM screens. This occurs because light reflecting off the paper is filtered more efficiently, resulting in less ‘whiteness’ from the paper reflecting into the eye.

Also, reprints are less likely because of the stability in controlling color on press. FM screens are much less likely to be impacted by ink density variations on press. The ink film on press is much thinner and less likely to be affected. Notice in the enlargement photo above the ‘pooling’ of ink in the conventional halftone dots. This causes the press to use more ink than is necessary.

FM Frequency          AM Frequency

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Stochastic Printing

Stochastic printing, also called frequency modulation (FM) screening, uses small (10, 20 or 25 Micron), same size dots in a random pattern and varies the density of the dot to create an image that is closer to continuous tone. In the reproduction of an image, we scan a continuous tone original photograph. The scan results in light striking a photosensitive device which issues a number that digitally represents the tonality of the original image. Printing a halftone image on paper requires that this number be passed to a computer, which stores a grid of numbers in a rectangular matrix representing the original image in digital form. To convert the digital matrix of numbers into a printed halftone, the computer sends the grid of numbers to the imagesetter where it is overlaid with a "virtual" halftone screen, a mathematical matrix. The computer captures the value of the numbers and passed it to the halftone generator in the imagesetter. The numbers can range from 0 to 256, which is translated by the halftone generator into a halftone "dot". That dot may exist in any of 256 potential values. The dot is actually drawn by the halftone generator that determines its shape as it grows in size from nonexistence to solid. Varieties of dot shapes exist, from round or elliptical to diamond shaped. In addition, straight-line and star-shaped dots are also possible. Stochastic printing uses a random dot, which takes the mathematical value of the dot and distributes its components inside the halftone cell. Stochastic patterns make possible halftone printing without the use of conventional dots. As a result, problems associated with screening striped or finely detailed fashion sportswear that would result in a moir patterns are eliminated. This also makes it possible to print in more than the conventional four colors of ink. By removing the barriers of screen angle interference from the printing process, stochastic printing has made it possible for the use of more than the basic 4 ink colors. Pantone introduced hexachromatic inks (six process colors). This allows more accurate reproduction of pastel colors.

NOTE: Screening is the process after rasterizing PDF files in the RIP (raster image processor) during prepress. Halftone screening is done through software and creates very small dots, or cells, that are imaged onto a printing plate. The tiny dots create the illusion of continuous tone photographs when printed on press.

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