Knocking Out Overprint Issues 
Friday, June 30, 2006, 01:47 PM - Registration
The purpose of the overprint feature on most graphic design programs is to make small black text and detailed black objects look sharper when using offset 4-color printing. Since not all black text is on a white background, it makes sense to overprint it on top of the other colors. There are, however, good and bad ways to use this feature.

See this example:

If this is what you want your finished product to look like, the black will print sharper if the fill is set to overprint. (Make sure your PDF settings preserve overprints)

Black channel turned off, no overprint:

Use the seperations preview to see what the document looks like with the black channel turned off. If it looks like the above image, the text is knocked out of the background and it is not overprinting. This makes registering the black to fill the white space difficult, and is not as dark.

Black channel turned off, with overprint:

It should look like this with the black channel off when it is overprinting correctly. The text does not have to be registered to the other layers and will print darker.

Don't overuse overprints:
-Do not use overprints for fill colors other than c0,m0,y0,k100
-Do not use overprints on large text or large black solids, especially when it is halfway off a background. (see example below)

The 12pt text would look fine overprinting. The larger 24pt text would look noticably bad because you would see the darker black where it is above the background.
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The Microcosmos of Printing (Registering Small Colored Text) [thanks Tony for the name] 
Friday, June 30, 2006, 01:18 PM - Registration
This entry actually came about through an e-mail correspondance with a customer, so I will just present it in that fashion.

Hey Matt, I remember how we talked about it being hard to use rich black for smaller fonts. So Im wondering if there is a difference if I want to use a color build for small text sizes? (lets say that C/100, M/57 Y/0 K/12 you told me about) I'd like to use this blue for some text but the size is about a 12 pt condensed gill sans. What are the issues with printing small colored text sizes? does it basically have to be put on using a single plate, so to only be possible with a pantone color?

If the font is a color instead of black, it must be registered on press, making it more difficult, but still totally possible. For production sake, I would not recommend it for paragraph after paragraph of small text (below 8-12pt.), unless it uses 2 or less process colors predominately. In most cases, it can still be done, but with more care on press. Colored small text printed process will never be quite as sharp, as black or single process color text.

cool, that makes sense. So that leads me to another question. Do you not register all press jobs? I am under the assumption that all jobs done on the press are registered. If a job is unregistered, does it mean you guys just throw the plate on to the press, without worrying about matching each plate exactly, but they are still fairly well aligned? and registered means that you run it through the press and adjust each plateposition till they fit perfect (or close to perfect) during the makeready stage?

We register all jobs to within a tolerance of a few microns. However, over the distance of a press sheet, other factors sometimes fall into play. For instance, as the sheet passes through the press, every printing unit that it passes through squeezes the sheet, causing the sheet to stretch slightly. By the time that the sheet reaches the last printing unit, the cumulative sheet stretch has actually made the sheet slightly longer than it was when it first went into the press. We add staggered packing to the printing cylinders, in an attempt to lessen the problem, but as different thickness of paper are used, the best that can be achieved is a happy medium for all stocks.

While the registration might only be off a fraction of a thousandth of an inch, when we are looking at extremely fine text, this deviation can cause the colored text to look "fuzzy" when closely inspected. If all of the extremely tight registration on the sheet is grouped into one area, the sheet stretch, will not affect the sheet enough that it can bee seen with even a loupe. When the tight registration covers the whole sheet, we must split the difference, and try to make it look the best that it can. Other factors that affect sheet stretch include, integrity of the paper stock being used, amount of ink coverage, even the humidity/temperature in the room. To wrap things up, we take great care to register all print jobs to an extremely tight tolerance, but there are some limitations to the physical manufacturing process. In short, understanding how offset printing works, allows designers to better set-up files to be reproduced more faithfully, and with fewer problems on press. The easier a job is technically, the more the operator can focus on color, and quality control; instead of just trying to make the job work on press.

Wow, what a trip. Printing presses and microcosmos. It just keeps going deeper and deeper down the rabbit hole. Yeah, I keep asking you all these questions so I can understand this better, thanks a million.
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Have you Ever Wanted to Just Choke Your Text? (rich black part 2) 
Tuesday, June 6, 2006, 06:54 PM - Registration
As I discussed earlier in the article "To Rich Black or Not to Rich Black", printing large black solids can be really disapointing unless "under-color" inks are added to the black ink, to achieve greater density, thus darker black tones. While the addition of process inks to black builds, help solve this problem (I recommend 60C 50M 50Y 99K), some additional problems can arise with Rich Blacks. Some of these potential problems were covered in the previous article, but there is one more issue that I felt was worthy of it's own discussion topic.

Choking text. What the heck is choking text? Why bother to choke my text? How do I choke my text? These are some of the questions I will attempt to answer with this entry.

While Large black solids can carry a lot of impact, and be quite cool in their own right, sooner or later, most graphic designers usually want to include some text in their designs. On a solid black background, most of the time, this text will be a white reverse, or at least a light color reverse. When working with rich blacks, this can pose some regestration issues, particularly when the text is small, or set in a serif font. The last thing that anyone wants when designing a showpiece brochure is to have the reverse text out of register, or "fuzzy" on the edges. Choking your text is like taking out an insurance policy that your small reverse text will look its best.

If you do not Choke your text, do not be surprised to discover that your fine text reverses turn looking like this graphic.

When there is no reason that they can't look like this (if you just take the time to add a little choke).

How do I do this wonderful thing, you might be asking? Simple: Adding choke to your text is as simple as putting a single color black stroke (0C 0M 0Y 100K) around your reversed text.

By taking this simple step with rich blacks, being a micron or two out of registration on press will not fill in your text with the process "under-color". You can see how this works, by looking at the next graphic, which shows only the Cyan, Magenta, and Yellow plates. the black has been turned off to show the "choke" of the under-color.

When we view the black on top of the undercolor, it will not be quite as dark as the rich black, but if the choke is small enough, your eye will not pick it up. (the contrast of the black has been greatly exaggerated in this next image for demonstration purposes).

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