In color printing, print registration is the layering of printed patterns to form a multicolor pattern. Registration error is the "position misalignment in the overlapped patterns." [1] Machine components such as the print cylinder, doctor blade assembly, printing plates, stress/friction and more, affect the registration of the machine. [2] Inconsistencies among these components can cause the printing press to fall out of registration; that is when press operators will begin to see defects in their print. There are many different ways to achieve proper registration, many of which employ the alignment of registration marks (pictured right). Many press manufacturers have installed automatic register systems to assist the operator in getting the print back into proper alignment.[ citation needed ]
When printing an image or a package of some sort that has more than one color, it is necessary to print each color separately and ensure each color overlaps the others precisely. If this is not done, the finished image will look fuzzy, blurred or "out of register" (see image to right). If one or more print units, plate or other print component is out of registration, the result can be printed colors in the wrong areas, overprint or white space. With proper registration, there will be no white space, out of margin colors, or confusing overlap of images in the print. To help line the colors up correctly, a registration system is necessary. [3]
In printing, registration black is a black color that includes 100% of each of the process colors used. Typically these are cyan, magenta, yellow and black (CMYK), [4] but if different colors are used, registration black marks are made with all of the colorants (inks). [4]
Registration black is used for printing crop marks and registration marks. When proofs for each color are generated on separate pieces of film, use of registration black makes crop marks visible on all channels, providing a useful reference for alignment. A thin line printed in registration black can also be used to check whether the printing plates are aligned.
The PostScript printer description languages supports registration black, starting with PostScript language level 2. This is done by referring to a spot color with the special name All. This never generates a spot plate. Instead it marks all of the plates that are there. The All color space can be used with a tint value between 0.0 (no mark) to 1.0 (full intensity). Generally, only 1.0 would be used.
The name "All" might not be used in the user interface of a design program, especially outside English language speaking areas. However, the spot color must have the exact name "All". As a side effect, it is impossible in PostScript to create a normal spot plate with this name.
The Portable document format (PDF) also includes a spot color called All, with the same restrictions, starting with PDF 1.2. Note that a PDF spot color must also include a "tint transform" which translates spot values into a different color space for viewing on screen, or printing to printers without spot color support. There is no special rule for the name "All", so PDF creators must include a tint transform that converts to black in some color space, in order to maintain the same appearance as the final printed piece.
Knock-out without trapping | Knock-out with trapping | Overprinting |
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A remedy for slight misregistration is trapping. Trapping is a method of adjusting areas where two distinct, adjacent colors meet so that press misregistration won't cause white spaces. [5] Where two colours abut, the lighter colour is slightly expanded into the darker to create an overlap. This yields a darker outline, which is considered less objectionable than a white gap. A major exception to this is the case when opaque (colors that completely obscure colors printed beneath them) spot colors are used. Other colors, regardless of their relative luminance, are always trapped to (spread under) these spot colors. If several of these spot colors are used (a common practice in the packaging market), the order of printing layers rather than luminance is the decisive element: the first color to be printed is spread under the next color. The trap width is dictated by the maximum amount of misregistration of the entire workflow up to the press.
Black ink is set to "overprint" colors in the background. The difference is not visible since the lighter color is spread underneath the—almost—opaque black.
There are many different styles of registration for many different types of printing. These deal with stone lithography, as used in fine arts printmaking. [6]
This method, using small measured registration marks on both the stone and the paper, is very accurate and simple to do. The printer measures the exact size of the paper and the desired margins. Then marks are made at both ends of the sheet of paper, and corresponding marks (usually in the shape of a "T") are made on the stone. Then the printer matches the marks on the paper to those on the stone. This way many runs of different colors can be pulled exactly in line with one another, each of them measured from the same system of marks.
This method involves laying the paper on the un-inked surface, and making a pin-hole through both the bottom and top of the paper, being careful to make a mark in the stone's surface. Then the locations of the holes are transferred to each sheet of paper to be printed. When printing, one should place pins in each hole of a sheet of paper, and lower it onto the inked stone, placing each pin in its respective hole in the stone. This method can ruin paper by creating holes and if the holes get too large, they lose their function as registration devices.
This method relies solely on hand–eye coordination. Eyeballing can be found in other industries as well. The printer places the paper over the stone-image, measuring and judging registration by eye. This is not very consistent, depending on the person.
Cyan is the color between blue and green on the visible spectrum of light. It is evoked by light with a predominant wavelength between 500 and 520 nm, between the wavelengths of green and blue.
Lithography is a planographic method of printing originally based on the immiscibility of oil and water. The printing is from a stone or a metal plate with a smooth surface. It was invented in 1796 by the German author and actor Alois Senefelder and was initially used mostly for musical scores and maps. Lithography can be used to print text or images onto paper or other suitable material. A lithograph is something printed by lithography, but this term is only used for fine art prints and some other, mostly older, types of printed matter, not for those made by modern commercial lithography.
A mimeograph machine was a low-cost duplicating machine that worked by forcing ink through a stencil onto paper. The process was called mimeography, and a copy made by the process was a mimeograph.
Printmaking is the process of creating artworks by printing, normally on paper, but also on fabric, wood, metal, and other surfaces. "Traditional printmaking" normally covers only the process of creating prints using a hand processed technique, rather than a photographic reproduction of a visual artwork which would be printed using an electronic machine ; however, there is some cross-over between traditional and digital printmaking, including risograph.
The CMYK color model is a subtractive color model, based on the CMY color model, used in color printing, and is also used to describe the printing process itself. The abbreviation CMYK refers to the four ink plates used: cyan, magenta, yellow, and key (black).
Printing is a process for mass reproducing text and images using a master form or template. The earliest non-paper products involving printing include cylinder seals and objects such as the Cyrus Cylinder and the Cylinders of Nabonidus. The earliest known form of printing evolved from ink rubbings made on paper or cloth from texts on stone tablets, used during the sixth century. Printing by pressing an inked image onto paper appeared later that century. Later developments in printing technology include the movable type invented by Bi Sheng around 1040 AD and the printing press invented by Johannes Gutenberg in the 15th century. The technology of printing played a key role in the development of the Renaissance and the Scientific Revolution and laid the material basis for the modern knowledge-based economy and the spread of learning to the masses.
Halftone is the reprographic technique that simulates continuous-tone imagery through the use of dots, varying either in size or in spacing, thus generating a gradient-like effect. "Halftone" can also be used to refer specifically to the image that is produced by this process.
Flexography is a form of printing process which utilizes a flexible relief plate. It is essentially a modern version of letterpress, evolved with high speed rotary functionality, which can be used for printing on almost any type of substrate, including plastic, metallic films, cellophane, and paper. It is widely used for printing on the non-porous substrates required for various types of food packaging.
Chine-collé or chine collé is a printmaking technique in which the image is transferred onto a surface that is bonded onto a heavier support in the printing process. One purpose is to allow the printmaker to print on a much more delicate surface, such as Japanese paper or linen, that pulls finer details off the plate. Another purpose is to provide a background colour behind the image that is different from the surrounding backing sheet.
Subtractive color or subtractive color mixing predicts the spectral power distribution of light after it passes through successive layers of partially absorbing media. This idealized model is the essential principle of how dyes and pigments are used in color printing and photography, where the perception of color is elicited after white light passes through microscopic "stacks" of partially absorbing media allowing some wavelengths of light to reach the eye and not others, and also in painting, whether the colors are mixed or applied in successive layers.
Digital printing is a method of printing from a digital-based image directly to a variety of media. It usually refers to professional printing where small-run jobs from desktop publishing and other digital sources are printed using large-format and/or high-volume laser or inkjet printers.
Prepress is the term used in the printing and publishing industries for the processes and procedures that occur between the creation of a print layout and the final printing. The prepress process includes the preparation of artwork for press, media selection, proofing, quality control checks and the production of printing plates if required. The artwork is quite often provided by the customer as a print-ready PDF file created in desktop publishing.
Offset printing is a common printing technique in which the inked image is transferred from a plate to a rubber blanket and then to the printing surface. When used in combination with the lithographic process, which is based on the repulsion of oil and water, the offset technique employs a flat (planographic) image carrier. Ink rollers transfer ink to the image areas of the image carrier, while a water roller applies a water-based film to the non-image areas.
In offset printing, a spot color or solid color is any color generated by an ink that is printed using a single run, whereas a process color is produced by printing a series of dots of different colors.
Color printing or colour printing is the reproduction of an image or text in color.
In printing, trap expresses the degree to which ink already printed on a substrate accepts another layer printed on top of it compared to how well the substrate accepts that ink.
Rich black, in printing, is an ink mixture of solid black over one or more of the other CMYK colors, resulting in a darker tone than black ink alone generates in a printing process.
Risograph is a brand of digital duplicators manufactured by the Riso Kagaku Corporation, that are designed mainly for high-volume photocopying and printing. It was released in Japan in 1980. It is sometimes called a printer-duplicator, as newer models can be used as a network printer as well as a stand-alone duplicator. When printing or copying many duplicates of the same content, it is typically far less expensive per page than a conventional photocopier, laser printer, or inkjet printer.
In the theory of photography, tone reproduction is the mapping of scene luminance and color to print reflectance or display luminance, with the aim of subjectively "properly" reproducing brightness and "brightness differences".
Chromoxylography was a colour woodblock printing process, popular from the mid-19th to the early-20th century, commonly used to produce illustrations in children's books, serial pulp magazines, and cover art for yellow-back and penny dreadfuls. The art of relief engraving and chromoxylography was perfected by engravers and printers in the 19th century, most notably in Victorian London by engraver and printer Edmund Evans who was particularly good with the process, producing a wide range of hues and tones through color mixing. Chromoxylography was a complicated technique, requiring intricate engraving and printing for the best results. Less expensive products, such as covers for pulp magazines, had to be produced with few colours, often only two or three, whereas more intricate and expensive books and reproductions of paintings used as many as a dozen or more colors. For each colour used, a separate woodblock had to be carved of the image being reproduced.
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