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Graphic Industry Terms Defined by an Insider -- Part 1
Susan Coppola
Trade Show Graphics Division Manager
Image Craft
Resolution. Not the kind you make January 1st, but the necessary information a file must have to guarantee the best possible digital output. Original information is best. Start with capturing the image, shooting the photo or scanning print or film to the proper size for the desired output. Interpolation, res up, resample, whatever you want to call it, can take the image size only so far before you see degradation. For the very best, sharpest output, make sure you get the proper amount of pixels right from the beginning. Different printing devices require different dpi setups; call your favorite graphics provider for more information.
Raster Printing refers to the pattern in which pixels are printed along parallel scan lines running across the page. The ink delivery jets or lasers scan in lines from side to side, top to bottom. In inkjet printers, the print head moves back and forth across the paper, which advances only a fraction of the inkjet head width with each pass. In optical printers, like Lambda or Lightjet, a laser beam rapidly scans the light sensitive paper while the paper slowly moves forward. Raster graphics are resolution dependant. If scaled beyond the intended size, it will result in an apparent loss of quality.
Vector Graphics. The Print and Prepress Industries refer to vector graphics as lines or shapes. This type of digital art can easily be scaled to any size. Art programs such as Adobe Illustrator, InDesign and Corel Draw can create vector type graphics. Fonts can be “outlined” (vector) to make them completely scalable.
Continuous Tone refers to images that have a virtually unlimited range of color or shades of gray. Continuous tone photo printers, Lambda or Lightjet, for example, can print each dot at many different shades of lightness and darkness. There are 256 or more shades of color so that the difference between one shade and the next is imperceptible to the human eye.
Color Space. RGB (red, green, blue) or CMYK (cyan, magenta, yellow, black). RGB is generally the color space related to photographic output. The RGB color space has a larger gamut of the two. Gamut refers to that portion of the color space that can be reproduced in print. Some of the colors the eye can see can be out of gamut. This is a critical concept when setting expectations for your customers or yourself.
Bleed. It’s that extra, non-important image beyond the crop that insures the edge on your graphic is exactly as you expect it. When mounting to rigid substrates or printing direct to boards and especially when a graphic will be router cut, bleed is essential. Image Craft recommends 1/8” to ¼” bleed on most graphics.
PDF means Portable Document Format (for what it’s worth). The PDF was created by Adobe Systems for document exchange. A PDF encapsulates a complete description of a fixed layout including text, fonts, images and vector graphics. Through the use of the free Adobe Reader software, anyone can open and view a PDF file. Generally, PDFs are used for electronic proofing purposes for large format graphics. Recently, over the past year or so, many graphic designers save their native files as high resolution PDFs for output. Our digital prep professionals prefer art to be saved in their native programs and ask to reserve PDF for proofing guides only.
UV Printing. Ultra Violet reactive inks require a high intensity of UV light to initiate a chemical reaction for drying the ink quickly. Many consider UV printing a green solution because it is more energy efficient than heat dried solvent type printing. Without the use of solvents, there is a lack of VOCs (volatile organic compounds) released into the atmosphere. UV inks perform exceptionally well on recycled materials.
