Knockout Type - Bare Minimums

Problems with "Knockout" or "Reverse" type

When placing type in white (or another light color) on top of an image or a background tint,  I always take a close look at small point sizes, thin Modern fonts (like Bodoni or Didot) and thin versions of fonts. The risk is that if the width of the thinnest part of the font is too thin, that registration variations and/or ink gain will cause the type to fill in, rendering it illegible, or at least not looking as intended.

This is so much of an issue in printing that there has long been a section dedicated to the topic in the industry standard SWOP (Specification for Web Offset Publications) guidelines

Reverse type and line art should not be less than .007” (1/2 point rule) at the thinnest part of a character or rule. Reverse type should use dominant color (usually 70% or more) for the shape of letters. Where practical, and not detrimental to the appearance of the job, make the type in subordinate colors slightly larger to minimize register problems on the production press. Small type and fine serifs should not be used for reverse type. The surrounding tone must be dark enough to ensure legibility. —SWOP ® SPECIFICATIONS 2007 (SWOP ® 11th Edition) See the full guidelines here. 

In order make sure a file is prepared for successful printing, I've outlined some methods that use to I deal with overly thin reverse, or "KO" type.

How can I make sure I'm meeting SWOP specifications?

Zoomed in to 4000% in InDesign (maximum zoom), I use the Rectangle Frame Tool to draw a box to measure the thickness of the thin portions of the letterforms. In the screenshots here, Frutiger Neue Book is being used at 8.75 point size.

The capital L's vertical stem measures 0.011" wide, much thicker than the 0.007" required by the SWOP specs quoted above. However even sans serif typefaces will almost always have some variation in thickness between different parts of different letters. The height of the crossbar on the lowercase e measures only 0.008"—thinner, but still thick enough to meet specifications. This job printed digitally on coated stock on an HP Indigo and came out looking great.

What's the risk?

Art Directors will sometimes show me examples of tiny KO type that has printed decently, to say, "Why can't we do that?" You can't assume that your printed result will be the bast case scenario. It's safest to take all factors into account and work to ensure a successful result.

Here is a scan of a page of a catalog I got in the mail yesterday. The text is muddy, uneven, plugged up, etc.

What went wrong? A lot was working against them here: 

• They used thin serif type at text and caption sizes, set in white on a very dark portion of a photograph. 
• We don't know the density (total of all four ink channels added together) but it's a four -color black regardless. Darker/denser colors are a greater risk for KO type.
• Color plates are slightly out of registration. So little that you might not notice if the type wasn't so thin. This registration is probably within the tolerance for variation allowed by industry standards. If the type were thicker, you wouldn't notice the registration.

Solutions:

1) Change the font. Change to a font that is bolder, or a bolder sans serif.

2) Make the font bigger.

3) Change the design, so it's black type on a light background, by adding a box to enclose the copy.

But often, anyone looking at these kind of problems doesn't have the option to make what might be considered creative changes. The client may have already signed off, and the proofreader may have already read the approved copy, and you would want to avoid reflowing the text. So there is a fourth option.

4) Add a stroke to the type, making sure that the stroke matches the color of the letter itself.

Here's how the math works out. 

• SWOP minimum KO letter thickness is a half point or 0.007" which is seven-thousandths of an inch.
• There are 72 points in an inch, so 1 point = 0.014"
• When you add a stroke to an object, the width increases by twice the stroke width, as it runs around both sides of the shape.
• If your type is 0.005" wide, and you want to increase to 0.007", you can add a stoke that is 0.001" wide, or 0.072pt wide. 0.005 + (0.001 x 2) = 0.007

As long as the changes are subtle, and the thickness of the stroke does not significantly alter the character of the letterforms, you can use this method you can avoid any changes to the font style, as well as preserving the line breaks of your approved text.