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38 Cards in this Set
- Front
- Back
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Visible Spectrum or Light
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Wavelengths ranging from 400nm to 700 nm and contains all the colors we can see
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Electromagnetic spectrum
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consists of bands of different wavelengths ranging from radio waves to gamma rays.
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Screen Ruling
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the number of ruled lines per inch (lpi) on a halftone screen
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Halftone
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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
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Halftone Dots
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Round, square, elliptical
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STANDARD process color angles
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C= 15°; M=75°; Y=0°; K= 45°
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We don’t use these STANDARD angles in your screen printing project- why?
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To prevent halftone moiré
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Stochastic halftoning
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is a halftone method that creates the illusion of tones by varying the number of micro-sized dots in a mall area.
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Stochastic halftoning-Advantage
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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.
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Stochastic halftoning-Disadvantage
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tints or solid color areas can sometimes appear grainy because the tiny dots are not really replaced in a random pattern.
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Gray Balance
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The measures of cyan, magenta, and yellow required to create a gray scale without producing a dominant hue.
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Color Correction
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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
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Tone Compression
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The reduction in density that occurs naturally in the printed reproduction of an original.
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Gray component replacement- what is it, what does it do for screen printers?
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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.
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Film Thickness
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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 |
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Film Surface
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Glossy- smooth and shiny
Matte - rough and textured |
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Film Speed
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How easily it is exposed
ASA or ISO or DIN number specifications |
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DPI
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Dots per inch measuring units for image resolution; the number of dots a printing device can generate in one linear inch. (scanners)
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LPI
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Lines per inch-the screen ruling is the number of ruled lines per inch. (halftone screen)
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SPI
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Spots per inch and usually refers to imagesetter or plate setter resolution
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PPI
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Pixels per inch and usually refers to monitor resolution
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Calibration
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Setting a device to its best output state
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Linearization
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Setting a device so that it gives a linear dot output from 0% to 100%
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. Hybrid screening, what does it try to affect in printing?
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Dots which have more than one dot shape in the range from 0-100%.
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Image Enhancement
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(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.
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Gray component replacement- what is it, what does it do for screen printers?
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We replace the graying component with BLACK (so you don’t go brown).
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Characteristic curves- what do they look like for each type of film?
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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) |
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What are the layers that film is made of?
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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. |
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Processing chemistry
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- 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 |
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Densitometer
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A device used to measure the density or darkness of an image.
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What other imaging materials “act” like film and need exposure assessment?
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Thermal film/plates – developed by heat
Inkjet film-UV rays Ablation film/plates - exposed by burning away part of the image |
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Does a dot making device like an imagesetter always need to be linearized?
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yes, because it ensures that dots are the same from day to day.
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What are some measurements of resolution in our industry?
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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 ) -- |
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What is a tonal reproduction system made up of?
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prevenative measure to create the best quality of image.
compensating for dot gain. |
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What is an imaging grid for halftones?
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grid to determine the size of the halftone dot and the quality of the image
16X16 256 dots determines shape |
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UGRA
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Film based device with mirco line scales that is in more precise exposure determination of plates and proofing materials
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FOGRA
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measures halation
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autotype stencil exposure
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exposure calculator
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