_TERMINE__FOTOGRAFIA_DIGITALE_E_DESKTOP_PUBLISHING_(INGLESE)
_SPIEGAZIONE_DEL_TERMINE_(INGLESE)
ADDITIVE COLOR
A colorspace in which light is added to black to achieve a color and tone. RGB is an additive color system in which Red, Green, and Blue light are combined to make white.
ALPHA CHANNEL
is a mask channel in addition to the three Red, Green, Blue image channels that can be used to isolate a particular area of an image in order for the computer to perform operations on that particular area. Alpha channels are used to describe silhouettes that have soft edges. (see: Clipping Path
ARRAY CAMERA
a digital camera that uses a large CCD chip (an array of rows and columns of light sensitive pixels) to sense the entire image at one time as opposed to scanning the image one row of pixels at a time.
ARTIFACT
any artificial glitch or blemish inadvertently created in or by the digital process.
BANDWIDTH
refers to the amount of data that can be transferred over the Internet in a given amount of time. A 14.4 kbps modem has a very narrow bandwidth and is very slow. A T-100 ISDN link has a high or broad bandwidth and is very fast.
BIT-MAPPED
images represent the artwork as a grid of colored dots called Pixels. Paint and image-editing programs such as Painter and Photoshop are bit-mapped images. (See also: Rasterize and Vector Graphics)
BIT DEPTH
The number of binary data bits used to record the brightness of each pixel per color channel. To achieve the illusion of ``continuous tone" requires 256 levels of brightness from black (0) to white (255). This requires 8 bits binary. Since it takes three channels (Red, Green, Blue) to represent color, we need 24 bit (3x8) color to achieve ``full color" RGB output and 32 bit color for CMYK. A bit depth of 48 (16 bits per channel RGB) records 65,536 levels of gray per channel. If the number given for bit depth is greater than 16 and is not divisible by 3 then it is probably referring to 4 channel CMYK.
BLEED
When a picture extends to the extreme edge of a page it is said to bleed. A full page bleed has an image covering the entire page with no borders. In order to give the printer some leeway in trimming a page with a bleed image you need to provide an image that extends beyond the crop marks. This extra area is called bleed and is usually 1/8 or 1/4 inch.
BLEEDING-EDGE
Beyond the cutting-edge of technology. A company that is accustomed to working in the experimantal fringes out beyond the cutting-edge is very capable of producing work that is state-of-the-art.
BRIGHTNESS
The apparent level of light emitted by or reflected from an object. The Brightness Range of an image is measured from the darkest black to the brightest white.
BUBBLE JET
Ink jet printers spit out very tiny spots of ink onto paper. The new Epsom printers delivering 1400 x 700 dpi with improved 6 color ink cartridges produce exceptional results. Properly profiled they produce proofs that are almost contract proof quality. The fifth and sixth colors are lighter Cyan and Magenta inks.
CALIBRATION
the process of adjusting a monitor or scanner to a repeatable standard. A monitor is adjusted to a specific contrast (Gamma), brightness, and whitepoint color balance.
CAPTURE
a digital camera is said to Capture an image rather than Take a picture.
CCD
a Charged Coupled Device is a type of electronic solid-state semiconductor device that is extremely sensitive to light. These devices are assembled on integrated circuit chips into either long rows for scanning devices or into arrays of rows and columns for digital and video cameras.
CHARACTERIZATION
the process of building a Look-Up-Table (LUT) for a calibrated monitor. By profiling the output of numerous key colors from a monitor a LUT can be created that allows the computer to substitute corrected (Characterized) colors to achieve consistent and accurate output.
CLIPPING PATHS
are vector defined outlines used to silhouette an object. They are created from ``Bezier" curves and are ideally suited in describing the hard edge outlines of mechanical or man-made objects. A clipping path is a particular type of path that instructs the RIP to ignore any part of the image outside of the path. If you want to place a file over another object or background in a page layout program such as Quark-Xpress then you will have to use a clipping path to eliminate the white that surrounds the image.
COLORSPACE
There are numerous methods of creating or describing a specific color and tone. These different models are called Colorspaces. examples are RGB, CMYK, LAB, YCC.
COMPOSITE COLOR
Proofs are proofs of completed pages and are assemblies of typography, graphics, and images. (see Loose Color
CONTINUOUS TONE
images use pixels instead of halftone dots. That is to say that rather than simulating variations in tone by increasing or decreasing the size of closely spaced spots of 100% ink or pigment color a continuous tone (CT) image is able to print or display continuously varying levels of pigment. To achieve the perception of a smooth (continuous) tonal transition from black to white it is necessary to have 256 differentiations of tone from black to white. If you have significantly fewer differentiations the human eye will begin to perceive breaks between the tones which will result in posterization and banding in the gradients.
CONTRACT PROOF
A proof the printer promises to be able to match on press.(See: Matchprint
CONTRAST
the difference and distribution of light and dark tones in an image. An image having mostly black and white tones is said to be contrasty whereas an image composed mostly of middle gray tones would be considered to be flat. The measure of contrast is called Gamma
DESKTOP
refers to computer and imaging systems linked to personal computers (PC's) such as Apple Macintosh or Intel Pentium computers as opposed to larger workstation type of computers such SUN or Silicon Graphics. Desktop systems use operating systems such as Macintosh OS, or Windows 95. Workstation systems typically use UNIX or Windows NT
DIGITAL
The process of representing and processing information that has been converted to binary numeric data. A digital image is made up of rows and columns of individual picture elements (pixels). In a full color RGB image each pixel is encoded as three 8 bit binary numbers which represent the brightness level each of the three colors (RGB). Because the entire image is recorded as a vast array of numbers it is possible for a computer to perform calculations on those numbers in order to manipulate the images.
DISPLACEMENT
Camera displacements are a feature of Large Format studio cameras that allow the relationship between the film plane and the lens plane to be altered in order to alter and control the perspective of the image. By using displacements it is possible, for example, to look up at a building and keep the vertical sides of the building parallel without having the keystone effect normally experienced with a camera.Digital cameras do not work well with significant displacements. The control of perspective is often best left to be accomplished in Photoshop
DITHERING
When a monitor cannot display intermediate colors or tones it attempts to achieve the required color by intermixing the two closest colors in a scattering (dithering) of pixels. This occursmost often when you attempt to display a full color image on a monitor with a 256 or a 64,000 color video display board. In an illustration dithering can make typography almost impossible to read.
DOT
Strictly speaking a dot is the smallest spot an imagesetter, or printer can output and is usually expressed in dots per inch (dpi). However the term dot is often used interchangeably with Pixels (ppi) or Halftone Cells (lpi or L/S). An imagesetter dot is of a specific and unvarying size. A 300dpi laser printer can only make dots that are 1/300 of an inch in diameter. To make a bigger spot it uses several dots. On the other hand, a halftone dot varies in size in order to simulate continuous tone. (see: Halftone)
DPI
Dots per Inch - The measurement of resolution for page printers, phototypesetting machines and graphics screens. Currently graphics screens reproduce 60 to 100dpi, most page printers work at 3-600 dpi and typesetting systems operate at 1,200 dpi and above.
DOTS PER INCH
The measurement of resolution for page printers, phototypesetting machines and graphics screens. Currently graphics screens reproduce 60 to 100dpi, most page printers work at 3-600 dpi and typesetting systems operate at 1,200 dpi and above.
DURATRANS
A large color transparency printed from a color negative and usually used in backlit displays such as trade show booths.
DYE-SUBLIMATION
A type of continuous tone printing process that produces a vibrant 300ppi color print. The pixels are printed by a thermal print head that sublimates (vaporizes) the dye from a colored saran wrap like ribbon onto the dye-sublimation paper. The hotter the element on the thermal printing head, the darker the spot of color.
DYNAMIC RANGE
The dynamic range or Optical Density of a scanner is a measure of the range of densities and the deepest shadow density that the scanner can see into and record information. If the dynamic range of the transparency exceeds that of the scanner then the scanner will perceive everything beyond its range as black. A Drum Scanner with a Dynamic Range of 3.8D and a bit depth of 48 will produce a much higher quality, richer, more detailed scan than a Flatbed Scan with a Dynamic Range of 2.5D and a bit depth of 24 at the same scan resolution.
EPS
A file format using the PostScript language and including a screen preview of the artwork, making it useful for desktop publishing. - Encapsulated Post Script - a file format used for images (see File Formats )
FAQ
Frequently Asked Questions
FPO
For position only. A small low resolution image that is used only to show the size and position of the final object, usually used either because the final object is too large or because the high resolution version is not yet available (see Stock art, OPI ). - For Position Only - A low resolution image file used for placement in page layout programs. The low-res file is small so that it doesn't slow down the machine and is used for position only. It is swapped out for the high resolution file when the page is RIP.
GAMMA
the measure of the contrast of an image or imaging device.
GAMUT
the range of colors and tones a device or colorspace is capable of recording or reproducing. The human eye can sense many more colors than can be reproduced on a computer monitor in RGB colorspace. The human eye has a larger Gamut than the computer monitor.
GIF
A file format popular on the world-wide web because of its small size. Limited to 256 colors, therefore not generally suitable for prepress. See JPEG, TIFF. - An indexed color file format. (see: File Formats)
HALFTONE
An illustration reproduced by breaking down the original tone into a pattern of dots of varying size. Light areas have small dots and darker areas or shadows have larger dots. - In order to simulate the reproduction of continuous tone images with ink on paper it is necessary to convert the continuous tone image into a halftone image. Black ink is just that...black. To print a gray tone from black we print many closely spaced black dots on white paper. The dots are so small that the eye doesn't see them so what it does see is the mixture of black ink dots and bare white paper between the dots which appears to be gray. A 50% gray would have dots sized so that they covered half of the area with black ink and left half of the area as bare paper. In order to effectively simulate continuous tone we need to be able to reproduce 256 levels of tone between black and white. So for a halftone image we need to be able to print 256 different sizes of dots. An imagesetter varies the size of the halftone dot by printing clusters of much smaller dots. To print 256 different sizes of halftone dots an image setter divides the area up into halftone cells that are 16 imagesetter dots wide by 16 imagesetter dots high. (16x16=256) If, within the boundaries of this halftone cell the imagesetter prints 128 black dots then you have a 50% halftone dot. So if an image setter is capable of printing 2400 dots per inch then the highest line screen you can output is 150 lines per inch (2400/16=150).
HISTOGRAM
A vertical bar graph displaying the distribution of the tonal values of the pixels in an image. The X axis represents the tonal value of the pixels (0-255) and the Y axis represents the number of pixels having that tonal value.
INDEXED
Color A type of color file that uses only one channel and assigns one of 256 colors to a pixel. Sort of like Paint-by-Numbers approach to color. The quality is poor...but the files are really small...good for the web.
INK JET
Ink jet printers spit out very tiny spots of ink onto paper. The new Epsom printers delivering 1400 x 700 dpi with improved 6 color ink cartridges produce exceptional results. Properly profiled they produce proofs that are almost contract proof quality. The fifth and sixth colors are lighter Cyan and Magenta inks.
INTERPOLATION
is the process wherein the software calculates the new value of a pixel based on an examination of the surrounding pixels. For example, when you enlarge an image the computer has to make-up the pixels that arent actually there. If you make a 4 x 5 inch image into an 8 x 10 image (having the same resolution) the file is four times larger. To do this the computer has to invent three out of every four pixels. If it simply makes the three new pixels the same value as the one original then the image will start to look blocky like a mosaic. To avoid this the computer looks at the surrounding pixels and, using some pretty sophisticated image enhancing mathematical magic (courtesy of the Department of Defense), interpolates the correct values for the new pixels. (Sort of an educated guess)
IRIS
Iris printers are extremely sophisticated Ink Jet Printers that spit out droplets of ink that are as small as red blood cells! (1/2000 of an inch) Iris printers are very popular not only as proofing devices but also for making fine arts quality limited editions on specialized papers such as heavy water color stock. These are often called Geclee prints (pronounced ``gee-clay")
JPEG
A file format using a compression algorithm developed by the Joint Photographic Experts Group. Very popular on the world-wide web and usable (but not common) in prepress. See GIF,TIFF. - A compressed file format. (see: File Formats)
KODAK APPROVAL PROOF
A digital proofing method that accurately simulates a halftone proof from a digital file without having to make halftone separation films.
LASER PRINT
A laser printer works in a fashion similar to a copying machine. It uses a laser to write an image on an electrostatically charged drum. Wherever the laser strikes the drum an electrostatic charge is created. This charge attracts the fine toner powder which is then fused with heat onto the paper.
LIGHTJET
A LightJet printer uses Red, Green, Blue Lasers to write a continuous tone image onto photographic printing paper in a similar manner to a film recorder. LightJets can produce high quality prints 48in. wide by however long.
LINESCREEN
The number of halftone cells per inch expressed as lines per inch (lpi)
LOOSE COLOR PROOFS
are proofs of individual images that have not been assembled into page layouts. (see; Composite Color)
LPI
Lines per inch. A measure of the halftone screen. In general, the LPI of the halftone is determined by the DPI of the output device and the number of shades of grey needed (due to the need to combine printer dots into a halftone cell). A common imagesetter outputting at 1270dpi x 1270dpi can produce 256 shades of grey at 133 LPI, while a 300 dpi laser printer can only produce 14 shades of grey at 53 LPI.  
MATCHPRINT
A Matchprint is a printers Contract Proof made from the same halftone negative film that will be used to burn the actual offset printing plates. It is called a contract proof because the printer promises to be able to make the printed page match the Matchprint. Other, similar, contract proofing media are FujiPrint, PressMatch, and Cromalin Proofs.
MONITOR
A computer Display screen. A monitor is an RGB display device.
OUTPUT SIMULATION
Output Simulation Mode is a feature color management software that allows you to accurately simulate on the monitor display what you will get on the printed page. This is accomplished by applying the profile of the specified output device and the monitor profile to the image file to appropriately limit the gamut and gamma of the displayed image. (see: Color Management )
PHOTOSHOP
A program from Adobe, now dominant in image editing, touching up photos, etc. - is the most popular Digital imaging software program. It allows for the color correction, tonal adjustment, sizing, and cropping of digital image files. It is also enables you to do retouching, image manipulation, compositing, and special effects.
PIXEL
A digital image is made up of small continuous tone spots called pixels. The word pixel is derived from the words Picture Element. In an RGB image (with a Bit Depth of 24) each pixel can be any one of 16.7 million colors/tones. Each pixel is made up of three color channels (Red, Green, Blue) and each channel can be any one of 256 levels of tone (256 x 256 x 256 = 16,777,216)
PLATE
Paper, polyester, or metal sheet used in a printing press to transfer an image onto paper. - An Offset Printing plate is a metal plate photo-etched from the halftone separation negatives.
POST
Production: A term taken from the motion picture industry which refers to all of the editing that takes place after the actual shooting of film.
POSTERIZE
To achieve the impression of continuous tone we need to reproduce 256 differentiations of tone from white to black. If we break down the tonal range into fewer differentiations you begin to see the breaks between the individual tones. We call this posterization, it often appears in smooth color gradients. Postscript is a software printer description language used in typography, graphics and page layout programs that allows vector graphics to be rasterized (RIPed) for output on a printer, imagesetter, or film recorder.
PPI
Pixels per Inch. A more precise term for DPI; usually used in discussion about image editing, such as in Photoshop.
PRE
Press: The process of preparing images, illustrations, and page layouts to be printed. Including scanning, separations, image manipulation, retouching, imagesetting, and proofing. (See: Post-Production)
PROFILE
An ICC description of a particular imaging input or output device that allows the Color Management Software to apply the proper color transformations to the image file to match the specific limitations of the device.
RASTERIZE
To convert vector graphic artwork into bit mapped artwork
RESOLUTION
The measurement used in typesetting to express quality of output. Measured in dots per inch, the greater the number of dots, the more smoother and cleaner appearance the character/image will have. Currently Page (laser) Printers print at 300, 406 and 600dpi. Typesetting machines print at 1,200 dpi or more. - A measurement of the amount of detail in an image file as measured in units per inch such as dpi, ppi, or lpi: Dots per inch, Pixels per inch, or lines per inch. Sometimes resolution is measured in units per millimeter. a ``Res 14" file would be scanned in at 14 pixels per millimeter which would be equivalent to 355.6 ppi (14 x 25.4 = 355.6)
RIP
Raster Image Processor. A device or program that converts electronic files into a pattern of dots the output device can display. All output works with dots. Vector art, halftones, and outline fonts are rendered as a pattern of dots by the RIP. - Raster Image Processing: to rasterize a file for output. When a page layout document such as a Quark file is RIP'ed all of the page elements (typography, photography, Illustrations, and Graphics) are assembled and rasterized into a Bit Mapped image to be output. It is in the RIP that the halftone screens are applied to the artwork.
SCANNING CAMERA
a digital camera that uses a single row of CCD sensing elements to scan the image one row of pixels at a time.
SIMULATION
Output Simulation Mode is a feature color management software that allows you to accurately simulate on the monitor display what you will get on the printed page. This is accomplished by applying the profile of the specified output device and the monitor profile to the image file to appropriately limit the gamut and gamma of the displayed image. (see: Color Management )
SLIDE
A 35mm color transparency.
SOFT-PROOF
The process of using the computer monitor to accurately simulate what the image will look like when printed.Proofing on screen rather than with a hard-copy contract proof. Soft-proofing is only possible when using accurate color management systems and output simulation display modes.
SUBTRACTIVE COLOR
A colorspace in which colored pigments are added to white paper. We start with White (paper) which is the presence of all colors and use Cyan, Magenta, Yellow pigments to subtract from the image to achieve black. The pigments subtract colors from the white light reflected off the paper. Yellow ink looks yellow because it absorbs (subtracts) everything except the yellow from the white light that is illuminating the page leaving on the reflected yellow light.
TAGGED IMAGE FILE FORMAT
A common format for interchanging digital information, generally associated with greyscale or bitmap data.
TIFF
An image file format. (see: File Formats)
TIFF (Tagged Image File Format).
A high-quality graphics file format suitable for desktop publishing and prepress and capable of retaining information about various color depths and resolutions. Compare to JPEG,GIF,EPS.
TONE
Tones are changes in apparent brightness of a color. (see: Continuous Tone)
TRAP
Trapping involves the addition of dots or pixels around the edges of an object so that you dont get white or colored gaps if the image is printed slightly out of register. This is necessary where two process colors meet but do not overlap. The trap causes a slight overlap.
UNSHARP MASKING
is a process where by the perceived sharpness of an image is enhanced by increasing the contrast along the edges where different tones meet.
VECTOR GRAPHICS
use mathematical descriptions rather than rows of colored dots (Bit Mapped). Vector based graphics represent objects as geometric shapes; straight lines, arcs, etc. They can be scaled and rotated without a loss in quality. Vector graphics are used for ilustrations and typography. Postscript is a vector graphic software language. Programs like Adobe Illustrator, Aldus Freehand, and CorelDraw are vector programs
WEB PRESS
An offset press that uses a continuous roll of paper rather than individual sheets (Sheet-fed). Web Offset is of lower quality then sheet-fed printing but is common where the press runs involve very large numbers of copies. Because the paper is a continuous roll and is moving very fast it is more difficult to achieve accurate registration.
WHITEPOINT
The whitepoint of a color display monitor is the color temperature of the monitor. The color temperature is stated in degrees Kelvin (K) and represents how warm or cool the white of the monitor is. Uncalibrated monitors generally have a very blue white (often as high as 9300K) The printing industry uses a standard called D5000 which is 5000K and closely resembles Daylight.
WINTEL
A computer running Windows on an Intel processor chip....your basic PC clone.
XEROX
A generic name referring to the output from color laser copiers (CLC's)
YCC
A colorspace used in Photo-CD that is somewhat similar to LAB color in that it uses a Luminance channel to define the tones and details of the image. YCC also uses two chrominance channels to define the color of the image.
