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Printing Digital Images

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Printing Digital Images – PowerPoint PPT presentation

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Title: Printing Digital Images


1
Printing Digital Images
2
Two Ways to Obtain Prints
  • Print them yourself
  • Use a printing service
  • Local
  • Online

3
Doing Your Own Prints
  • Three type of printers available
  • Inkjet
  • Color Laser
  • Dye Sublimation

4
How Color Images Are Printed
  • Color printers create images by dividing a page
    into thousands, or even millions, of tiny dots,
    each of which can be addressed by the computer.
  • As the printer moves across and down the page, it
    can print a dot of color, print two or three
    colors on top of each other, or leave the spot
    blank (white).

5
The Two Basic System for Creating Color
  • The two basic system for creating color are
  • additive
  • Subtractive
  • Additive color is used by color displays to
    create the images you see.
  • Additive color uses red, green and blue added
    together in various amounts to create all of the
    colors

6
Additive Color
  • Additive color is used by color displays to
    create the images you see.
  • Additive color uses red, green and blue to create
    color images on the screen.

7
Subtractive Color
  • Color printers use the subtractive color system
  • The primary subtractive colors are cyan, magenta,
    and yellow.
  • By using one or more of the subtractive primaries
    on a dot eight different colors can be produced.

8
Colors from Subtractive Primaries
Color 1
Color 2
Color 3
Combined
White
White
White
White
Cyan
None
None
Cyan
Magenta
None
None
Magenta
Yellow
None
None
Yellow
Cyan
Magenta
None
Blue
Cyan
Yellow
None
Green
Magenta
Yellow
None
Red
Cyan
Magenta
Yellow
Black
9
  • A black ink is added to the subtractive printing
    system.
  • This provide a deeper black then can be created
    by the combination of cyan, magenta and yellow
    alone
  • The name for this color system is CYMK, K being
    the black component.

10
Halftones and Dithers
  • On most printers (dye-sub is an exception), each
    printed dot has the same density of color.
  • If the printer only combined these solid colors,
    it would be limited to the eight primary colors
    for reproduction.
  • To get the millions of colors in a photograph,
    the printer has to "fake" the colors by
    generating a pattern of small dots that the eye
    blends to form the desired shade.

11
  • This process is called halftoning or dithering
    and is controlled by the printers software.
  • designing printer software that does halftoning
    well is as much art as it is science.

12
  • Halftoning is done by arranging the printable
    dots into grid-like groups, called cells
  • then using these larger cells as a single unit to
    print pixels with
  • Each cell may be 5 by 5 or 8 by 8 dots in size.
  • The primary colors are combined in a pattern of
    dots in these cells, and the eye perceives them
    as intermediate hues.

13
  • For example, to print purple the printer uses a
    combination of magenta and cyan dots. For less
    saturated hues, the printer leaves some dots
    unprinted and hence white in color.

14
Inkjet Printers
  • There are two types of inkjet printers that can
    print photographs
  • The standard inkjet printer that uses four inks,
    cyan, magenta, yellow and black
  • Photo inkjet printers that can have seven or more
    inks including cyan, light cyan, magenta, light
    magenta, yellow and black.

15
Part of an Inkjet Printer Print Head Assembly
  • Print head - The core of an inkjet printer, the
    print head contains a series of nozzles that are
    used to spray drops of ink.

16
  • Ink cartridges - Depending on the manufacturer
    and model of the printer, ink cartridges come in
    various combinations, such as separate black and
    color cartridges, color and black in a single
    cartridge or even a cartridge for each ink color.
    The cartridges of some inkjet printers include
    the print head itself.

17
Print head stepper motor
  • A stepper motor moves the print head assembly
    (print head and ink cartridges) back and forth
    across the paper.

18
Paper Feed Assembly
  • Paper tray/feeder - Most inkjet printers have a
    tray that you load the paper into.

19
  • Rollers - A set of rollers pull the paper in from
    the tray or feeder and advance the paper when the
    print head assembly is ready for another pass.
  • Paper feed stepper motor - This stepper motor
    powers the rollers to move the paper in the exact
    increment needed to ensure a continuous image is
    printed.

20
Control Circuitry
  • A small but sophisticated amount of circuitry is
    built into the printer to control all the
    mechanical aspects of operation, as well as
    decode the information sent to the printer from
    the computer.

21
Printer Quality
  • Determined by the dots per inch that can be
    printed by the print head.
  • Also depends on how many tones or colors can be
    generated in each cell

22
How Droplets Are Created
  • Link to flash movie

23
Color Laser Printers
  • Are more expensive the Inkjet printers
  • Supplies are more expensive
  • The quality of photos approach the quality of a
    good photo inkjet printer
  • Have a problem producing glossy prints.

24
Dye Sublimation Printers
  • Where picture quality is very important,
    dye-sublimation printers are best.
  • The "dye" in the name comes from the fact that
    the process uses solid dyes instead of inks or
    toner
  • Sublimation" is the scientific term for a process
    where solids (in this case dyes) dyes are
    converted into a gas without going through an
    intervening liquid phase.

25
Materials
  • Dye sub printers have their colored dyes in a
    transfer roll or ribbon. This roll contains
    consecutive page-sized panels of cyan, magenta,
    yellow and black dye.
  • These printers require special paper that's
    designed to absorb the vaporous dye on contact

26
How it Works
  • During printing, separate passes are made across
    the print for each of the four colorscyan,
    magenta, yellow, and black.
  • A thermal print head, consisting of thousands of
    heating elements, contacts the media being
    printed on and vaporizes the solid dyes.

27
  • What makes these printers unique is that the
    heating elements on print head can be set to any
    one of 256 temperatures.
  • The hotter the temperature, the more dye is
    transferred to the paper.
  • This precise control of the amount of dye that's
    vaporized controls the density or intensity of
    the resulting dot on the paper and produces
    continuous-tone images.

28
  • Because the dyes are transparent, a cyan dot may
    be printed on top of a magenta dot to make a blue
    dot.
  • By varying the amount of C, Y, and M, any color
    within the printer's color range may be produced.
  • Because they can vary the density of each color,
    dye-sub printers are the only ones that don't
    have to use halftoning or dithering to create a
    wide range of colors

29
Printing Your Own Pictures VS Printing Services
  • Printing your own pictures advantages
  • Quicker turnaround
  • Control over result
  • Printing your own pictures disadvantages
  • Cost
  • Convince

30
  • Photo Service Advantages
  • Cost
  • Ease of printing
  • Size of prints
  • Photo Service Disadvantages
  • Instant gratification
  • Control
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