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Graphic Communications
GRA 424

GRA424 MIDTERMTOPIC 1 PRINT CHARACTERISTICS DensityMeasured by densitometer logarithmic equationsLots of light reflected backlow density light colourLittle light reflected backhigh density dark colour40highest density readingreads CMYK onlypantone spot light metallic colours are not read accurately by a densitometerif measuring a pantone reddetect as the nearest colour magentathe densitometer reads all 4 colours reading from the highestlowestthe amount of ink laid down affects density dot gain print contrast ink trapDot AreaDot gain the increase in size of a printed dot from plate to press sheetTheres also dot gain in prepress from film or film to plateDot gain is always up to 125 patch on plateDot gainTVI tonal value increaseThe densitometer has a filter measuring the opposite filter colourRGBCMY RMY GCY BCMTarget values o highblack more dot gain o lowyellow less dot gain o middlecyanmagenta 50 dots have more dot gainInk Trapping ndnd The ratio of a 2 down ink film onto a previously printed ink film relative to the 2 down ink film on paperIn offset lithography the thickness is 35 um microns ndst The 2 laid down colour is a lower thickness than the 1 laid down colourInk trap affects colour on the printed sheetMust know colour sequence to do calculationsOnly care about the 2 colours that make up our overprint RGBits easier to print ink on paper than another colourink trapping is never 100ratio of ink film laid down form previous ink filmlaying down a thick ink film plateaus because at a certain point you will achieve colour that will not change in densitythe ratio represents the thickness percentage of the first aid down ink ie 8080 thicknesswetdry trapif ink was wet or dry before being overprintedink trap influences ink tack ink film thickness ink temperature time between impressions printing press design inkwater blanace paper absorbency Print Contrast RatioThings that may reduce print contrast are paper colour type dot gain low ink densitySoupy ink more dot gainThick or hard ink less dot gainPractical method to establish a target ink film thicknessRequires solid density and 75 tint density
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