Halos are Evil*

The general consensus among designers is that halos around text detract considerably from a design. The most common reason that map makers employ the halo technique is to provide added emphasis on text or to make the text legible on highly saturated and complex backgrounds.

However, when a halo—particularly of the “large and lumpy” type—is used, it subverts and obfuscates all the typeface designer’s original work. No longer does the spacing, shape, consistency, x height, vertical stress, apex form, incline, and counter size make sense. In short, it looks bad.

*As with any “rule”, this idea of halos looking bad is more nuanced than I’ve initially let on. Small halos, where the color of the halo matches the map’s background color, can be effective in allowing the text to be more separated from other intervening layers such as roads.

Let’s see this in action. Just to make things interesting, the example is of a very difficult situation involving a complex tree height LiDAR analysis, a riparian corridor, and a creek name label. There will be other cases that will be more simple than this, and in those, simply get rid of the halo or change the font’s size or color to achieve the kind of emphasis and contrast that you need.

Here’s the initial set-up with no halo. It is difficult to read:

To make the creek name stand out more, you might try a mega halo. This results in visual catastrophe:

Another option might be to make a smaller halo. Halos in Arc default to white. Most simply stick with the default, as in this example, which still doesn’t work:

Finally, a solution that does work. Changing the small halo color from white to the same green that makes up most of the color that is behind it, visually separates without drawing undue attention:

In some cases, a halo of this type won’t work if the map reader will be scrutinizing every pixel that lies near the text. In this example, the map reader might misinterpret the light green halo as representing more of the equally colored tree-height pixels, incorrectly thinking there is more of that tree-height category than there is. For a map meant to be read at close-range for visual analysis, such as this one, the light green halo is not the ideal solution. Other maps will not have this problem (for example, if the background was a solid ocean polygon). The solution for this map is to get rid of the halo completely and lighten the saturation of the tree-height layer.

  1. #1 by Amanda Taub on November 14, 2012 - 3:17 pm

    What about using halos on road names over aerial photos? The background color is not consistent. What are your thoughts?

  2. #2 by Todd Lusk on November 14, 2012 - 3:41 pm

    Lighten the aerial photo overall and the labels will stand out more. Often the aerial photo isn’t the focus if the map anyway.

  3. #3 by Gretchen on November 15, 2012 - 10:53 am

    Agreed. Lightening the aerial photo is usually the best option. Black and white aerials are the worst because they alternate frequently between pure whites and pure blacks. You could try decreasing the image’s contrast value to lessen that, probably along with also increasing its transparency. A bold black text with a very narrow halo might be the only option on a fully saturated background. It looks like Charlie Frye has some things to say about this too.

  4. #4 by Gretchen on November 15, 2012 - 12:23 pm

    I don’t usually post twitter responses to posts in the comments but I loved this one from @fulfilledstraw: Before reading the latest blog post from @PetersonGIS , I thought my halos were great. I don’t even know who I am anymore…

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