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.
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.