Understanding Dotted Stroke Styles in InDesign

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InDesign’s Stroke Styles, especially the dotted stroke styles, are a mysterious topic; and for good reason. The Adobe InDesign Help File offers just basic instructions on how to create custom stroke styles, but essentially no information on the logic behind how they work. This article is dedicated to demystifying the dotted stroke styles. To access the Stroke Styles dialog box, click on the Stroke panel flyout menu, then choose Stroke Styles.

InDesign offers three types of dotted stroke styles: two are built-in (Japanese Dots and Dotted), and the third (Custom Dotted) is found in the New Stroke Style dialog box.

But before I start explaining the difference, I want to acquaint you with the terminology used when discussing InDesign’s dotted stroke styles. I like to name my Custom Dotted stroke styles with this terminology in mind. Note that I have named this example: “15/30, Adjust Gaps.” I find that naming the stroke style like this tells me exactly what I can find in the stroke styles dialog box, without having to open the dialog every time just to see how the stroke style is constructed.

Center: According to the Adobe Help file: the “Center” is where the center of the dot is positioned. However, that is only completely true when the stroke has no corner adjustment. More on that later.

Pattern Length: The length of the repeating pattern. A smaller pattern length will mean more dots, closer together. A larger pattern length will mean fewer dots, farther apart.

Corners: You can choose either “Adjust Gaps” or “None.” This has to do with how InDesign handles dot placement across the line.

Note: The stroke styles unit of measurement is based on the InDesign’s default unit of measurement. For an explanation of how to change your stroke styles units to display in points, please read my article at InDesignSecrets, The Elusive Stroke Style Units of Measurement.

In addition to the options in the Edit Stroke Style dialog box, there are a few other attributes affected by stroke styles, namely Cap and Length. Because the Cap type affects the length of the line (and therefore how many dots the line will have), it is important to understand these attributes.

How Caps Affect Line Length in Stoke Styles

With a solid stroke, the Projecting Cap and Round Cap options extend the visible length of a line past its endpoints. The length of the line shown in the Transform and Control panels reflects this. With the Butt Cap option, the line ends (both visually and mathematically) exactly at the line end points. So in this case, a butt cap line with end points 100 points apart is exactly 100 points long.

With both Projecting and Round Caps, the length of the line (both visually and mathematically) is longer than the distance between the two end points. In this case, a 10 point thick line with end points 100 points across will result in a line 110 points long.

Note that Custom Dotted stroke styles seem to defy this logic!

The Discrepancy Between the Transform Panel and Reality

A Custom Dotted stroke has Round end caps. Because of this, it will make a line look longer than one of the built-in strokes (Dotted or Japanese Dots). This is because the dots on each end of the line project outward. So a 10 point thick line will have 10 point diameter dots on each end, centered on each endpoint of the line. These end dots project 5 points out past the end of the line. I suspect this is a bug, because if you inspect the coordinates of a 100 point long line that has one of the built-in stroke styles applied to it, the end points will actually only be 90 points apart. Remember with a Solid stroke style, the end cap type affects both visual and mathematical properties of the dot. But with Custom Dotted stroke styles, the Projected end caps add to the visual appearance of line length, but do not affect its actual length shown in the Transform and Control Panels.

To actually get a Custom Dotted line to look the same length as one of the built in dotted stroke styles (Dotted or Japanese Dots), you’ll need to subtract the thickness of the stroke from the length of the line. In this case, my strokes should be 100 points long. So to get my 10 point thick Custom Dotted stroke to visually appear 100 points long, I need to set the length to 90 points.

And if Japanese Dots, Dotted, and Custom Dotted stroke styles weren’t quirky enough, I found that you can actually change the end cap so that you get little bits of gap color peeking out the ends. At first, I thought this wasn’t possible since since the cap options are grayed out with Dotted stroke styles. But the trick is to change the stroke style to Solid, then change the Cap type to Projecting, and finally change the Stroke Style back to Custom Dotted. Voila! Square ends! This trick also works in reverse, in case your dotted stroke has square ends and you need to change them back to round ends.

A Very Brief History of Built-In Dotted Strokes

For years, curious InDesign users have wondered what the difference is between Japanese Dots and Dotted. Thus far, the only conclusion is that Japanese Dots are closer together than Dotted. However, in doing research for this article, I found something much more interesting: how the built-in stroke styles are different than a Custom Dotted stroke style. 

Custom Dotted

There are two main corner options to consider when creating a Custom Dotted stroke style: Adjust Gaps and None. Unless you understand this difference, you may end up going crazy trying to make a precise and controllable Custom Dotted stroke style.

Corners: Adjust Gaps

Choose Adjust Gaps to have InDesign sacrifice precise dot spacing accuracy in exchange for nice looking corners and line ends. Custom Dotted with Adjust Gaps will always require an odd number of dots. Interestingly, the built-in stroke styles are set to adjust gaps, but do not have the restriction to only have an odd number of dots on line segments.

Corners: None

Choose None for the corner adjustment to have InDesign follow your Center and Pattern Length numbers exactly (resulting in icky-looking corners and ends if your math isn’t perfect). 

To get dots that are immediately adjacent to each other with no space in between, set the pattern length to double the Center and the stroke weight to the same value. For example:

Center = 10

Pattern Length = 20

Stroke Weight = 10.

Understanding Custom Dot Spacing Logic

Studying the various custom dotted strokes has confounded me for a very long time. After much experimentation, mathematical patterns emerged in how many dots are in a line segment.

Custom Dotted, None: When increasing the stroke length, white space (or gap color) will be added to the end of the line to accomodate the width of an entire dot. (The width of a dot is equal to the thickness of the line.)

Custom Dotted, Adjust Gaps: the width of the line must exceed the number evenly-divisible by the Center before another dot is added. The space in between the dots simply expands or contracts as needed, until the dot number can change. This range is shown in the table below.

Japanese Dots, 10 pt thick line

Custom Dotted 20/40, Adjust Gaps, 10 pt thick line

2 Dots: 0–40 pt long

3 Dots: 0–60 pt long

3 Dots: 41–60 pt

5 Dots: 61–100 pt

4 Dots: 61–80 pt

7 Dots: 101–140 pt

5 Dots: 81–100 pt

9 Dots: 141–180 pt

6 Dots: 101–120 pt

11 Dots: 181–220 pt 

7 Dots: 121–140 pt 

13 Dots: 221–260

 

 

Dotted, 10 pt thick line

Custom Dotted 15/30, Adjust Gaps, 10 pt thick line

2 Dots: 0–55 pt long

3 Dots: 0–45 pt long

3 Dots: 56–85 pt

5 Dots: 46–75 pt

4 Dots: 86–115 pt

7 Dots: 76–105 pt

5 Dots: 116–145 pt

9 Dots: 106–135 pt

6 Dots: 146–175 pt

11 Dots: 136–165 pt

7 Dots: 176–205 pt 

13 Dots: 166–195 pt

I hope that having a better understanding of the various types of dotted stroke styles will encourage you to use them in your designs and be less frustrated when doing so. Now if anyone out there knows what makes “Japanese Dots” Japanese, would you please enlighten the rest of us?

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