Output
- Densitometer
- A device used to measure light absorbed by a piece of film or
a substrate. A transmission densitometer is used for film and will
read out density and halftone dot percentage. These devices are
used to calibrate an output device. A device called a reflective
densitometer is used to measure reflective surfaces such as a
proof or a press sheet.
- Density Adjustment
- The first step in calibrating an output device. Density
adjustment is accomplished by adjusting laser exposure and film
development characteristics. Results are measured with a
transmission densitometer which is used to measure the density of
the film coming from the output device and developed in the
processor.
- Emulsion Up/Emulsion Down
- Emulsion is the chemical coating on film that holds the image.
This term describes the orientation of the emulsion when looking
at the film and reading the type on it. Depending upon other
prepress steps, it will be appropriate to create film that reads
correctly (versus mirror image reversal) when the emulsion is up
or when it is down. Sometimes abbreviated RREU or RRED standing
for "right reading emulsion up (or down.)
- Film
- Material that is loaded into an imagesetter. Film is coated
with a light sensitive emulsion and exposed with laser light
inside the output device. After chemical development the film
holds a very sharp image of the layout created by the designer.
This film is used to prepare printing plates for a press run.
- Hardcopy
- Hardcopy is the generic term used to describe the materials
containing images of our layouts and artwork that come out of a
laser printer or an imagesetter.
- Imagesetter
- An output device containing a laser that is used to form an
image on film from desktop files. Particularly, an output device
equipped with a PostScript RIP to interpret commands in the
PostScript language.
- Laser Printer
- (Some, but not all Laser Printers have PostScript
capabilities.) A hardware device found in most offices that uses
laser technology to form an image that is transferred to paper. It
is toner particles (like a copier) that actually mark the page.
Laser printers have an attribute of Resolution that is expressed
as DPI (dots per inch.) 600 DPI lasers are most common but there
are specialized lasers with greater resolution.
- Linearization
- A term referring to part of the calibration process for an
imagesetter. Linearizing is the process by which one makes sure
that a requested 40% halftone dot will output and measure as a 40%
halftone dot. An output device is typically linearized by
outputting a test file containing small patches of grey in 5%
steps from 0% to 100%. Each patch on the resulting film is
measured with a transmission densitometer and recorded in the
calibration software. The resulting settings become a filter
through all future files are output.
- On-line Processor
- For the development of film coming from an imagesetter, an
on-line processor is connected directly to the imagesetter and
exposed film is automatically carried from the imagesetter into
the various chemical baths required for processing the film. It is
generally considered preferable to have an on-line processor
because it eliminates the need for the operator to hand carry
exposed film to a remote processor.
- Output Device
- A printer. The term is most often used to describe a
high-resolution imagesetter that is used to output desktop page
layouts to film negatives.
- Paper
- A term used for the material that is fed through a laser
printer. Also refers to the photographic material that can be used
in an imagesetter as an alternate to film.
- Plotter
- An alternate term for an imagesetter. See imagesetter.
- PostScript
- A page description language described by its creator (Adobe
Systems) as "the language of desktop publishing." The PostScript
language is a programming language spoken by desktop software
after the "print" command is issued. These PostScript instructions
created by the software (in partnership with the printer driver)
are sent to a PostScript laser printer to describe the page the
user wishes to have output. The PostScript laser printer has an
interpreter inside (called a RIP) that takes that page description
and instructs the laser how to image the page.
- PostScript Dump
- The act of printing a page layout to a disk file rather than
printing directly to a PostScript laser printer. This allows the
user to transport the file to another location and download it to
a PostScript laser printer. See PostScript.
- PostScript Error
- An event that occurs during the printing of a page layout. A
PostScript error can occur when a page is too complex or it
contains an element that has a technical defect. When a PostScript
error occurs, the printing of that file terminates and usually no
hardcopy emerges. To troubleshoot the problem, an individual
knowledgeable in the PostScript language can (often) analyze the
error and know where in the page layout to look for the
troublesome element.
- PostScript File
- A file created by printing a page layout to a disk file rather
than printing directly to a PostScript laser printer. This allows
the user to transport the file to another location and download it
to a PostScript laser printer. See PostScript.
- Print Command
- The command, present in all software that initiates the
process of creating hardcopy. See also PostScript.
- Print PostScript to Disk
- The act of printing a page layout to a disk file rather than
printing directly to a PostScript laser printer. This allows the
user to transport the file to another location and download it to
a PostScript laser printer. See PostScript.
- Printer Driver
- Important computer software that facilitates communication
between software and the output device. See also PostScript.
- Processor
- For the development of film coming from an imagesetter, a
processor contains the various chemical baths required for
processing the film.
- Resolution of an Output Device
- Resolution of an Output Device is expressed as DPI (dots per
inch) and refers to the number of laser spots per inch. It is
generally considered that having output resolution of 600 DPI or
above is important for attractive but achieving quality halftone
reproduction relys on having much more resolution than that. A
properly formed halftone dot will require a resolution many times
higher than the halftone ruling. (A 150 line screen is best when
output at a resolution of 2540 DPI.) This is why quality
imagesetters have peak resolutions measured 3000 DPI and above.
- RIP
- Raster Image Processor. A RIP is a part of a PostScript laser
printer and part of a PostScript imagesetter. It is a special
computer that converts PostScript page descriptions into a
rasterized image that can be edited or output directly. (A page
layout must be ripped before it can be output.) See also
PostScript
- Ripping
- The act of processing a PostScript file on a RIP. See also RIP
- Service Bureau
- An organization (frequently born out of an existing
typesetting business) equipped with PostScript imagesetters and
providing simple output services. Typically solicit business with
low prices and quick turn-around times.
- Spooler
- A term referring to a specific productivity boosting software
utility. A print spooler manages the print out function for the
user and allows the user to regain control of their computer much
faster than without. Also, a spooler will often coordinate print
jobs received from many users sharing a particular laser printer;
storing each print job in a "print queue" and sending them to the
laser one at a time.
- Spot Size
- A term referring to the smallest element an imagesetter marks
onto the page. Measured in microns, these spots are the building
blocks that are used to create letter forms and halftone dots.
When one refers to the resolution of an imagesetter (expressed in
DPI) one is referring to the matrix in which these spots are
imaged, not particularly to the size of the spot itself. Modern
imagesetters have several spot sizes available for specialized
purposes such as stochastic screening.
- Stochastic Screening
- Stochastic screening is a halftoning technology available in
certain Output Devices where very small dots are positioned with
varying spacing. Putting dots closer together simulates darker
areas and putting them farther apart simulates lighter areas.
Considered much harder to output and proof, there are two benefits
to the user: Greater detail in any photographic image printed with
Stochastic film. Elimination of screen angles allowing process
color printing with more than four inks. Each imagesetter
manufacturer has their own trade name for their Stochastic
Screening technology.