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Lecture

GRA 533 Week 13 Trapping

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Department
Graphic Communications
Course
GRA 533
Professor
Abhay Sharma
Semester
Fall

Description
GRA 533 November 25, 2013 Week 13 Spot colours can’t be simulated properly as CMYK Slide 3 – what is trapping? • Done in final stages when it goes to print • Provides margin of error • In indesign you call it a stroke  ▯stroke should be centered and the colour of the stroke  should change according to the colours ▯ has o be minimally visible • If it’s a rough printing process it will move more, if it’s fine then it will move less • Overprint  ▯will overprint the different layers on top • Knockout ▯ nothing underneath • Stroke is the easiest way to do trapping o Border of margin o Center it • All printing processes misregister slightly • Rough printing processes require a greater stroke • A ring or donut around the border so if it moves slightly it’s covered o Should be centered o Overlap minimum visible o Slide 5 • Should know how to set them • InDesign and Illustrator have an overprint preview Slide 6 – trapping in InDesign • Attribute palettes, can turn it on or off for the profile • By default everything is knockout • Stroke is on the inside and is centered ▯ it’s the default • Spread and choke are reversed • The stroke allows us with a buffer that won’t allow white paper to show through Slide 7 – trapping theory • Darker colour distorts the lighter colour Slide 8 – trapping theory • ­individual plates  • what’s on each separation  o if they fall on top of each other and that causes misregistration problem and that’s  why we fix it in prepress o need to know how much they move • What we care about is how many separations there are and how they will move relative to each other • Colours don’t matter the ink does (CMYK) 5. Should not be trapped as they’re printed on the same plate o Slide 9 – trapping theory o Doesn’t matter what colours they  are  o Slide 10 – trapping theory o If the same colours are being printed on the same plate it won’t misregisiter and there  won’t be any white space  ▯this won’t be trapped Slide 12 • When two objects comprised of different inks/separations touch – then trap • When on the same plate – there is no need to trap Slide 13 – how much trapping? o Won’t be asked on final quiz o Lpi is related to the quality of printing process o We know the quality of the printing process  ▯so we know how much the thickness of the  stroke needs to be  o Can be figured out 3 ways, through trial and error on printing (many industry  people do this), ratio of lines per inch through the equation, tabulated values from  the book • LPI is related to the qua
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