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Printing Knowledge for Prepress Printing: Color Separations
Printing Knowledge for Prepress Printing: Color Separations
In order to reproduce or prepare a full color image for printing using four process colors, the image must be divided into the the individual subtractive primary color components. The separation process can be accomplished photographically or electronically.
Photographic Separations: Using a large process camera, a full color image is converted into halftone negatives which contain a series of dots of various sizes to represent shades of gray. The dots are achieved with the use of special screens placed over the negative material during exposure. When printed, the smaller dots create the lighter areas of the image, with the lightest appearing white, and the larger dots make up the darker areas of the image, with the darkest appearing black. This system of using the halftone screens directly with the film is known as the Direct Screen Photographic Color Separation method. A halftone negative is made for each of the separate subtractive color components of the image (cyan, magenta, yellow) and black. The four halftone negatives are records, in varying shades of gray dots, for each of the separate color components and are known as "Color Separations".
Another photographic technique known as the Indirect Photographic Color Separation method is also used. The original image is separated into the individual primary color components and continuous tone films are made for each of the separations. From continuous tone films, the halftone negatives or positives are created. The advantage in first creating continuous tone separations before creating the halftones is that the continuous tone separations can be reduced or enlarged and corrected before the actual halftone films are produced.
Color separations created from photographic methods are used to prepare analog plates for traditional printing methods. Each plate corresponds to one of the four colors, cyan, magenta, yellow, or black. The plates are coated with the corresponding ink colors during the printing process and the inked image from the plates is transferred to the substrate. The varying sizes of the halftone dots on the plates determines the amount of ink that will be printed on the substrate. The dots from each of the different colored images overlap to produce the full color image.
Electronic Separations: The electronic separation of an image into its individual color components has become the most popular and labor saving method of producing color separations. The original image is placed in a scanner which stores the image as a digital record. The digital image can be imported into a software program such as Adobe PhotoShop™ where the color separations can be produced with the click of a mouse. The scanned image and/or the color separations can be quickly manipulated and edited in an infinite number of ways with the tools provided with the software. Color separations created electronically can be output to film to prepare analog plates or they can be used for Computer-to-Plate applications and digital printing. YellowPrinting: If you copied it to elsewhere, please show the original sourceof this article, thanks.
10 questions to test your printing knowledge: ( Answers can be seen the bottom part of this article, but do not peek before answering it by yourself, :) ) According to Gartner, printers, the supplies associated with them and the support required to keep them operating represent 5% of the typical IT budget. How much do you know about printers and related technology? Take our quiz to find out! Want to study up a little first? See our glossary of printing terms. 1. This term is what P.S. stands for on a letter. It's also the name of a programming language that describes the appearance of a printed page. What's the name of this term? 2. This printing method, which creates raised and colored areas on paper, is often seen in wedding invitations, business cards and letterheads. What kind of process is it? 3. Which of the following is the oldest form of printing: a. gravure b. flexography c. letterpress d. screen printing 4. In printing, DPI is the standard measure of prin
Ten Questions For Testing Your Knowledge Of Printing 1. For rush projects on an offset/traditional press, does uncoated stock or coated stock allow the ink to dry faster? A. Uncoated B. Coated 2. Small quantity projects are typically printed on a digital press. What is the maximum sheet size (including bleeds) that can be printed on our Kodak NexPress? A. 11" x 17" B. 12" x 20" C. 13.4" x 35.6" D. 28" x 40" 3. True or False: All 100 lb Cover paper is the same thickness. A. True B. False 4. What is the largest paper size we can run on our offset presses? A. 20" x 24" B. 23" x 35" C. 25" x 38" D. 28" x 40" 5. True or False: File preparation (graphic design) can be the same regardless of whether the printing method is digital press or offset/traditional press. A. True B. False 6. True or False: For short-run or variable data projects, digital press production is limited t
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