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38 Cards in this Set

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Visible Spectrum or Light
Wavelengths ranging from 400nm to 700 nm and contains all the colors we can see
Electromagnetic spectrum
consists of bands of different wavelengths ranging from radio waves to gamma rays.
Screen Ruling
the number of ruled lines per inch (lpi) on a halftone screen
Halftone
gives the viewer an illusion of a continuous tone image when it is actually a tone pattern composed of dots that vary in size, but not density
Halftone Dots
Round, square, elliptical
STANDARD process color angles
C= 15°; M=75°; Y=0°; K= 45°
We don’t use these STANDARD angles in your screen printing project- why?
To prevent halftone moiré
Stochastic halftoning
is a halftone method that creates the illusion of tones by varying the number of micro-sized dots in a mall area.
Stochastic halftoning-Advantage
provide greater definition and detail in irregular shapes and expand the range of tones that can be reproduced thorugh increased ink densities and improved color saturation.
Stochastic halftoning-Disadvantage
tints or solid color areas can sometimes appear grainy because the tiny dots are not really replaced in a random pattern.
Gray Balance
The measures of cyan, magenta, and yellow required to create a gray scale without producing a dominant hue.
Color Correction
Adjusting images to optimize values for highlight and shadow neutral tones, skin tones, and sharpness used to compensate for impurities in the printing ink and color separation
Tone Compression
The reduction in density that occurs naturally in the printed reproduction of an original.
Gray component replacement- what is it, what does it do for screen printers?
The removal of equal amounts of cyan, magenta, and yellow areas of a four color halftone and replacement of these colors with a higher proportion of black. This produces a less muddy effect.
Film Thickness
Base thickness if measured in mils
(thousandths) of an inch.
.004” film is common for smaller negative
sizes
.007” is common for larger negative sizes
Film Surface
Glossy- smooth and shiny
Matte - rough and textured
Film Speed
How easily it is exposed
ASA or ISO or DIN number specifications
DPI
Dots per inch measuring units for image resolution; the number of dots a printing device can generate in one linear inch. (scanners)
LPI
Lines per inch-the screen ruling is the number of ruled lines per inch. (halftone screen)
SPI
Spots per inch and usually refers to imagesetter or plate setter resolution
PPI
Pixels per inch and usually refers to monitor resolution
Calibration
Setting a device to its best output state
Linearization
Setting a device so that it gives a linear dot output from 0% to 100%
. Hybrid screening, what does it try to affect in printing?
Dots which have more than one dot shape in the range from 0-100%.
Image Enhancement
(refers to Resolution) the un-sharp masking tool- makes images sharper…looks at changing density and makes it a harder edge than what was originally there.
Gray component replacement- what is it, what does it do for screen printers?
We replace the graying component with BLACK (so you don’t go brown).
Characteristic curves- what do they look like for each type of film?
Characteristic curve (also called Gamma) reps the relationship between exposure and density. – how film reacts to light and development.
Separated into three parts—
Toe – (start of curve) intial response to exposure
Straight line ( middle of curve where is straight)—exposure ragnge that identifies the density development for each exposure.
Shoulder ( top of curve ) where more exposure will not increase density.
High contrast film curve-- Steep
Low contrast Film ( continuous tone)—more elongated (Density vs exposure)
What are the layers that film is made of?
Protective overcoat- anti-scratch material
Emulsion- chemical compounds that form a light sensitive coating – silver halides(compounds of silver and chlorine) suspended into gelatin
Adhesive layer- bonds emulsion to base
Base- Plastic or special grade paper—most use polyester base Others are Acetate base, polystyrene base and glass base
Anticurl/Antihalation backing- biodegradable dye coating that absorbs light rays so that light wont reflect and produce double image or shadow on the emulsion.
Processing chemistry
- Litho: Old Technology
Very high contrast, fragile chemistry
- Rapid Access
High contrast, durable chemistry
- Hybrid
Higher contrast, stable chemistry
- Heat (Thermal)
High contrast from heat causing chemical reaction
- Ablation- a laser blasts image area clear
High contrast
Densitometer
A device used to measure the density or darkness of an image.
What other imaging materials “act” like film and need exposure assessment?
Thermal film/plates – developed by heat
Inkjet film-UV rays
Ablation film/plates - exposed by burning away part of the image
Does a dot making device like an imagesetter always need to be linearized?
yes, because it ensures that dots are the same from day to day.
What are some measurements of resolution in our industry?
1 bit ( b&w) lineart or halftone ( 0 or 1) – clear or black
8 bit ( b&w) grayscale- 256 levels of gray
16 bit grayscale – 4096 gray tones
24 bit ( color) made of 8 bit of each RGB
32 bit (color ) --
What is a tonal reproduction system made up of?
prevenative measure to create the best quality of image.
compensating for dot gain.
What is an imaging grid for halftones?
grid to determine the size of the halftone dot and the quality of the image
16X16
256 dots
determines shape
UGRA
Film based device with mirco line scales that is in more precise exposure determination of plates and proofing materials
FOGRA
measures halation
autotype stencil exposure
exposure calculator