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About Ran
Expertise
My main area of continuous expertise with CorelDraw involves setting press advertisements and I have rarely used it to produce complex drawings. However as director of a small company I have amassed a good deal of background knowledge of computers, various printers and networks over the years. When it comes to problem-solving, I have a long history of having nobody to ask but myself and, lately, the internet!

Experience
About 20 years' experience in daily use, from version 1

Education/Credentials
University educated and over 2 decades of hands-on experience

My first printer was a Star LC10 Colour and I once paid £1745 for an HP Laserjet III.

You are here: Experts > Computing/Technology > Graphics Software > CorelDraw > Exporting Image dialogue options

CorelDraw - Exporting Image dialogue options

Expert: Ran - 10/22/2009

Question
Hi Again Ran,

Wanted to ask about the "overprint black" option given when you export a file to jpg or tif or whathaveyou - the export image dialogue box gives the option to select "always overprint black"
what does this mean? ... and what are the consequences, advantages and disadvantages of using this option?
Many thanks again Ran. Cheers!

Answer
Overprint Black is an option which applies to CMYK colour separations and means that when a *solid* black object is positioned over another colour, the colour layer is NOT "knocked out" to make way for it. Therefore when printing, the black ink is placed on top of the other colour. In theory the other colour is not visible because the black ink is so much stronger than it.

This is very useful in order to overcome registration errors in the printing process, where anything out of alignment would cause a partial white or other colour outline around the black object.

In particular I would almost always set the black to overprint when using particularly small black text over a background colour or image.

Modern printing presses have much finer tolerances than a few years ago and registration is generally very good. Some magazine publishers boast of "100% registration", by which they mean their plate alignment is absolutely spot on. However newsprint is a different matter and registration is damn difficult because the paper itself can stretch. It is common to see absolutely appalling registration in a newspaper and a designer who hasn't taken this possibility into account should be huddled in a corner weeping when the important parts of his advertisement are illegible due to his poor choice of colours or failing to overprint his black etc!

You won't see the overprint black option when exporting a bitmap (.jpg, .tif or even whathaveyou!) because a bitmap contains no colour separations, they are only a grid of pixels.

For proper control of overprinting I would recommend using it on an object-by-object basis, rather than the blanket option in the output dialog. Right-click your object and select Overprint Outline or Overprint Fill (and always overprint black when you have small black text on a coloured background). Remember that the object itself is unaffected by this, it only affects the behaviour of whatever lies below it.

"Trap" is a complex topic which I won't bore you with now, but it is when you slightly increase the size of an object and overprint its fill (or outline, or both) to take registration errors into account.

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