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Digital Photo Printing
By Ashish
Printing industries are increasingly adopting digital technologies to complement or replace analog ones. The terms digital and analog (or analogue) designate both types of signals for representing data and methods of print reproduction. Analog signals and computers use variations in continuous phenomenon such as voltage or pressure to transmit data, while digital signals and computers rely on discontinuous patterned transmissions of discrete amounts of electricity or light to communicate data.
Analog printing methods reproduce images with like images. Screen printing, for instance, is an analog print method that employs film positives and negative stencils which resemble the original image to create prints. Similarly, lithography uses analogous images on plates to transfer ink to print substrates. Flexography, etching, rotogravure and other analog print methods employ other forms of analogous image transfer. All of these methods reproduceimages from a master image. Unlike these analog printing technologies which use stencils or plates containing full sized images, digital printing approaches assemble each image printed from a complex of numbers and mathematical formulas. They configure images from a matrix of dots or pixels. These use digitally controlled deposition of ink, toner or exposure to electromagnetic energy, such as light, to reproduce images.
Both analog and digital image quality and print resolution involve a complex of phenomena. One needs to understand the relationship of these to compare different printing technologies effectively. Resolution is usually indicated with terms such as lines per inch (lpi), lines per centimeter (lpc), dots per inch (dpi), or dots per centimeter (dpc). Inkjet images are composed from a grid of pixels, i.e. picture elements or dots. The number of these dots per linear inch in the x direction and the number of dots per linear inch in the y direction indicate the dpi resolution of a print. Software can usually instruct a printer to construct its lines from one or more rows of contiguous pixels. If one used 4 pixels per line on a 360 dpi matrix, one would be printing 90 lpi output. In actuality these terms, dpi and lpi, describe only one aspect of what is termed apparent resolution, i.e. the resolution we perceive. Another factor is grayscale or gray levels. This involves the number of different sizes or grays a pixel dot in a matrix can have. In inkjet printing, this
involves the number of drops addressed per pixel or dot, or the number of possible droplet sizes per pixel dot. These are largely software rather than hardware factors. Digital printing addresses its ink or toner to a grid or matrix. Digital software image processing can offer a large number of matrix patterns including random patterning. It also permits a single master or print image to contain multiple matrices. For instance lettering might be generated in a pattern which favors line acuity, while a photographic image is generated in a pattern which permits the desired degree
DIGITAL PRINTING TECHNOLOGIES
Digital printing encompasses many technologies. These include various forms of inkjet, thermography, electro photography and electrostatic printing, iconography, magnetography, and digital photographic imaging and developing. None of these require a physical master but instead rely on digital data to create images.
About the Author
Ashish who is an expert in digital photo printing.
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