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Terms and Definitions
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| Bleed |
When a graphic image or type or a ruled line extends beyond the edge of the page or crop marks. The intent is that the image “runs off the page” or bleeds off the page. |
| Inposition |
Inposition proofs are made from the digital
file and is used to check final trim, folding, finishing requirements
as well as confirming that all elements of the created file have
been imaged properly. Changes or AAs (Authors Alterations) can
be made at this time, but there will be additional charges. This
is usually the most important proof and should be reviewed VERY
CAREFULLY. Things like text re-flow, missing images, correct
image arrangement or layering, final trim locations and size
should all be inspected, confirmed and approved. |
| Halftone |
An image that has been screened into a pattern of dots of varying sizes. Halftone usually refers to photographs and graphic images. |
| Live Image |
This refers to customer-supplied images that will be used “as is” for printing, i.e., the printer will not scan a photo and replace it with a hi-res image. |
| RGB |
The method of how color is defined on your monitor and by many desktop color printers. Usually Red, Green and Blue ink colors. This is NOT how the printer will produce your job (the printer will use the CMYK process). |
| CMYK |
Is the color process that is used in the printing process. All colors can be reproduced using Cyan, Magenta, Yellow, and Black ink. It is important for the customer to provide their files in CMYK color definitions, not RGB. The reason for this is that in some color combinations the translation of RGB color to CMYK color does visually change the “look” or appearance of the color. For this reason it is important that the customer convert their images from RGB to CMYK so they can evaluate this color shift and make any adjustments needed. |
| 4-Color Process |
The term used to indicate the color printing process. The printer will print using 4 colors of ink (Cyan, Magenta, Yellow, and Black) and depending upon the position and placement and size of the printed dots the human eye will see “full color”. Pantone ink colors that have been selected will be converted to a build of CMYK, i.e., if a line of type had been defined to print in PMS 185 red it would be converted to print as a CMYK build of 100% magenta and 90% yellow. |
| Spot Color |
The term used when a specially formulated and pigmented ink will be used by the printer instead of using the CMYK process. This is used most often when the job is a 1, 2, or 3-color job and is not a “full color” job. Spot colors are also used in conjunction with 4-color process jobs (CMYK) when the cmyk equivalent of a spot color does not closely match that spot color. Some examples of spot colors that do not translate well to CMYK are all metallic colors, PMS 172, many pastel colors and most fluorescent type colors. |
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Resolution and Rips
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Postscript
printers, imagery (processors), CTP devices and digital proofers
all build picture images by using building blocks called pixels
(for “picture elements”). These pixels form a virtual mosaic on a fine grid and form the pictures that we see in proofing and printing. To display an image the computer makes some of these pixels light and some dark. The finer the pixel grid, the higher the resolution. The resolution is expressed in “dots per inch” (d.p.i.). The higher the resolution the sharper and crisper the image will be printed. A low resolution will result in a “grainy or blurred” appearance.
To process your layout page, every Postscript device has an internal computer called a “RIP” (Raster Image Processor). The higher the resolution of an image the more pixels it contains and the harder the RIP has to work. Below is an example of pixel numbers as resolution changes from designer to printer:
Your low-resolution F.P.O. (for position only) image, given to you by the color separator or scanner operator for building your documents are usually at 72 d.p.i.. Thus a low resolution 8”x10” image has approximately 414,720 pixels.
Most laser printers print at 300 or 600 d.p.i. An 8”x10” image at 300 d.p.i. resolution has approximately 7,200,000 pixels. This is 17 times the pixels of a low resolution 72 dpi image.
A typical high resolution image setter used to produce film for your printing job will have a resolution of 2400 to 3600 dpi. An 8”x10” image will have 460,800,000 pixels – 60 times that of the laser printer and 1200 times more than the low-res 72 dpi image.
The confusion is caused here and can result in problems: All monitors are displaying the images and type using only “part” of the information that is contained in a file or graphic element. The maximum resolution of your computer screen is 72 dpi. SO…a 72 dpi low –resolution image will “look” very good to you when viewed on your computer screen. It may even look good when you print it out on your 300 dpi or 600 dpi printer. BUT when it is processed by the printers film imagesetter and printed at 2400 dpi there will not be enough “information” in the image for the RIP. The rip will use the information that is there and the result will be a “pixilated image”. How pixilated this image will be depends directly on the resolution.
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Scanning and Resolution Recommendations
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There are two basic types of images that are scanned: halftones (photos and art) and line work, cartoon type drawings, continuous tone elements such as one-color logos. Photos (grayscale or color) should be scanned at a resolution of 300 at the size they will be used in the document, example: If a photo is scanned at 100% at 300 dpi resolution and then placed in a document and reduced to 50% of that size all of the information of that original image is still in that graphic element…it now has a resolution of 600. Too much resolution is not a good thing. It can affect image quality and it can cause processing problems for your computer and the printers RIP.
Recommendations: 300 dpi for halftones and 1200-1800 dpi for line work (like type or one-color logos)
Warning: It is not recommended that you increase the resolution of an image by “re-sampling” in PhotoShop or some other graphic program. This re-sampling rarely results in an image with acceptable quality when you are trying to increase the resolution of an image. You can usually re-sample an image to a lower resolution and maintain the desired quality.
The types of images that will often not reproduce well are images “grabbed” off the web. These images are usually very low resolution and are designed only for quick loading and viewing….not for printing.
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File Formats
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| File formats can affect the final quality and the amount of time your jobs take to print on a RIP. Advising the client which one is best is still judged on an individual job basis. |
| TIFF |
The most popular image format for photos and scanned graphics. “Tagged Image File Format” saves images in a raster format. Raster formats are basically dot (pixel) representations. |
| EPS |
Encapsulated Postscript” is a highly transportable file format. Since it is already in Postscript it is easier to process and print. EPS files are “vector” based. This means that the image is defined by line formulas, the vector formulas allow images to be stretched and rotated without stretching or disfiguring the image. |
| JPEG |
This file format uses a specially designed compression formula that allows the file to “stay small” in size. This compression formula can affect the quality of a high resolution image. |
| GIF |
A very common format used extensively on the web. These files will rarely offer the quality and resolution needed for printing. They are designed for viewing only. |
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Fonts
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Fonts are the cause for most common problems associated with proper printing and imaging of customer provided files.
Fonts are small applications the manage type in a document. Each Postscript font is a precisely matched pair of programs called “screen fonts” and the “printer font”. To design a page on the computer, you will need the screen font, and to print the page out to any Postscript printing device you will need the matching printer font. There is a weakness to the two font process however, the RIP has to search for the corresponding printer font when it is processing a document. To do this it refers to the fonts name or font ID in the Postscript code. Since font names and ID numbers can change everyone must be vigilant that this does not happen. Providing the printer with a suitcase of the fonts used usually solves this problem. Below are some valuable tips about fonts.
When including bold and/or italicized type in your design use the actual Adobe font versions. If you use a menu command from your layout program (like applying bold or italic) to a highlighted area of type) you are very likely to be disappointed with the results. REMEMBER: the RIP uses Postscript language when it prints your file on film. Postscript does not reliably interpret menu applied type commands such as bold or italic. Example: You should use Adobe Garamond Italic instead of italicizing Adobe Garamond with a menu command.
It is legitimate to send a copy of your fonts to the printer for the purpose of printing your job. No violations of licensing are made when this is done.
A frustrating complaint that is heard too often from customers about fonts is “It prints fine on my desktop printer, I don’t understand why the printer cannot print it using his Postscript printers/imagers”. The reason is that Postscript printing devices require more and different font and graphic information than normal desktop type printers. This requirement for complete Postscript language is the cause of that frustration.
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What is the correct way to specify color?
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This question is one that needs to be answered BEFORE you give the job to the printer and is one that if not addressed costly errors can be made.
If your job is going to be printed in “spot colors” these colors are usually specified as PMS colors using the Pantone Color Library. Your color palette may offer some “standard” colors as a default setting. These colors may be called red, blue, green, yellow, etc. You probably do not want to use these colors as they are very poorly defined. In other words, we don’t know what shade or hue of red or blue or any color you are specifying. Be sure and define spot colors by using the PMS color you really want. Select SPOT and RGB when defining each color.
If your job is going to print in 4-color process (full color) you may use specified colors for such things as type, gradients, ruled lines, colorized tiffs, or tinted or filled boxes. When you define these colors use the Pantone system and define the colors as PROCESS and CMYK. When you do this you tell the printer that you want the process equivalent of the pms spot color to be printed; i.e. instead of using a 5th color spot pms 185 you have designed your job to use 100% magenta and 90% yellow which will look very much like pms 185.
Some jobs are designed to print in 4-color process plus 1, 2,3 or 4 additional spot colors are not uncommon. When you define the colors in your color palette you decide which colors are to be printed as process builds and which are to be printed as additional ink colors. The colors you define as SPOT and RGB will be printed as additional ink colors; and the colors you define as PROCESS and CMYK will be printed as process builds.
If your job is to be printed using any of the metallic inks you will probably want to make sure these inks are specified as SPOT COLORS as metallics do not translate well when printed in their process builds.
Make sure all the color images you have placed in your document are defined as CMYK if they are to be printed in 4-color process. DO NOT LEAVE THEM AS RGB images (most desktop scanners and digital cameras provide RGB color images). The reason you should convert your images to CMYK is that sometimes there is a color shift in some tonal ranges when you convert from RGB to CMYK – when you do the conversion to CMYK you will see the new color and be able to decide whether there has been a color shift that requires your attention.
If you have color images in your document but you want them to print as a grayscale (one color) you must convert them to grayscale from their current RGB or CMYK status.
NEVER define color images as Indexed Color, Lab Color or Multichannel. These image definitions do not translate well when your file is imaged on film. If you use any of these image definitions you will probably not like the color of the final printed product.
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