Hi everyone,
I use Corel Draw X7 in my sign making business and have no problems in doing my graphic design in Corel Draw and then pringing it on my 1.4 metre wide vinyl printer. However, I have a client who also wants 8000 pamphlets, as well as his signs. I want to upload the artwork for these pamphlets to a wholesale commercial trade printing service which requires it in PDF format for its automated (no humans involved) offset printing process. I rang them to make sure I formatted it correctly.
The pamphlet is essentially gold logo and text on a black background. (lets say yellow on black to keep it simple)
The concern the offset printing expert had was that the yellow and black would mix to result in a murky brown. As with all commercial print staff I have dealt with, he had no knowledge of Corel Draw, so he could not advise on settings to use in Corel when creating the pre-press PDF. He asked me how I was going to produce yellow print on a black background. I told him I would create an A4 sized rectangle and colour it black, and then layer the gold text onto that. He said that in offset printing you have 4 plates: C M Y K. The black rectangle would be just that on the K plate, a solid black rectangle, while the Y plate would just have the yellow text on it. The black would be printed first and then the yellow on top of that, resulting in the yellow being on top of black (unlike an office printer which only prints what you can see, with nothing behind it).
He said I need to ensure I specify "Knockout" in my PDF creation so the yellow characters of the text are "knocked out" of the black plate, and therefore black is not printed under the yellow text.
I have just about blown my brain Googling "Corel Draw Knockout", "Creating PDFs for offset printing", and other combinations of key words.
What does "knock out" mean in Corel terms, and does it have anything to do with the "Preserve all overprints" check box in the Publish to PDF (pre-press) dialogue box?
If anyone can tell me how to prepare a PDF from a CDR file to send to an offset printer I would be very much obliged to you.
Many thanks,
James
James,
By nature, the Key plate (usually the Black plate) usually prints last. So in general on most presses, the printing plates are printed in the order of the CMYK abbreviation. The screen shots below illustrate yellow on black and are from Acrobat. In the second one, I have shut off the yellow plate.
You can see that the black is knocked out where the yellow text is. In reality, most times there is not a pure Yellow but rather some CMY or CMYK mix...unless you are using a spot color. So it would not have been a pure paper color knockout if there is an CMY mix there.
jzelliott said:Under the "Color" tab in Publish to PDF (prepress), by default the check box next to "Preserve document overprints" is ticked - should I un-tick it?
If you don't use Overprint on your fills and/or oulines, no matter if you leave this box selected or not: There's not any overprint to preserve.
jzelliott said:Also, under the Color tab, the colours are set by default to output as "Native" - should I change that to CMYK?
If you use CMYK colors, it will output as CMYK, so there's no problem if you leave this option selected. If you use spot color, those color will output as spot