A few weeks ago, somebody wrote in to us asking about the best size and type of text to use on digital signage displays. At the time, I was researching various aspects of ADA compliance for interactive kiosk applications (which will be the focus of a future blog entry), and I came across some interesting information on the subject.
Not
surprisingly, there hasn't been a lot of research focused exclusively
on digital signage. However, our brethren from the world of
printed signage have spent a good amount of time, energy and money on
this very subject, so I think that it's only proper that we should
borrow some information from them.
But before we simply take the
tried-and-true rules of static printed signage and try to attach them
to their dynamic, electronic counterparts, it's important to look at
the differences between these two types of display media. For
example, most printed signs would fall under the heading of a reflective
display -- that is, ambient light bounces off of the signage material
(whether it be paper or vinyl or something else), and into the eyes of
the viewers. Reflective displays are good in high ambient light
conditions like daylight or bright indoor lighting. Likewise,
they don't work very well in poorly lit areas, since the dimmer the
ambient light, the dimmer the sign will appear. On the other
hand, most digital signs are emissive, in that they actually
produce their own light. Thus, they are most noticeable in
low-light conditions, since they would be brighter than their
surroundings, but they can get washed out in bright-light
conditions. Also, while a good, high-resolution digital sign
(like a plasma display or LCD monitor) might contain about 70 pixels
per linear inch, paper output typically has 300-600 dots per inch,
offering much higher resolution. This means more vibrant graphics
and crisper, easier to read text than electronic displays.
Having
gotten that out of the way, most of the design rules that apply to
static (printed) signage also apply to digital signs. For
example, the most obvious one: bigger text is easier to read, and can
be seen from further away. What's a good rule of thumb
here? As this article from Signweb
suggests, text one inch high can be seen clearly from 25 feet
away. You need to increase the size by about an inch (vertically)
for every additional 25 feet of visibility. A slightly different
take on visibility can be found here,
where the authors suggest that 3 inch-high text can be seen from up to
100 feet away, but will have maximum "impact" at about 30 feet.
This page also has, "[t]he exposure time for exterior signage is:
Drive-by traffic: 3 seconds, Walk-by traffic: 11 seconds."
Next,
think about the use of color and contrast on your digital
signage. Since you're likely to have moving images behind or next
to your text, the background color might change significantly while a
viewer is trying to read your message. Consider these words of advice from Signweb:
"[W]ords
that comprise initial capital letters followed by lower-case letters
are more readable than words that employ all upper-case letters. On the
other hand, from a greater distance, signs that incorporate all capital
letters are probably more legible.
Outlines and drop shadows can
also improve readability. For example, heavy, black, drop shadows can
create the right contrast and improve readability. Although black is
frequently used for drop shadows, it isn't the only color you should
consider. For example, if you're using gold lettering on a bright-red
background, use a dark red for the shadow -- the dark red will soften
the transition from the gold in the foreground to the red background."
Finally,
while many principles of static signage do apply to dynamic digital
signs as well, some decidedly do not. For example, it is common
wisdom that a serif font is easier to read (and therefore allows for
greater comprehension and recall) than a sans-serif font. (For
those who are not typographically inclined, this is a nice primer on typeface terminology).
While this is true in the print world, it is not true for digital
signs, where sans-serif faces reign supreme. The main reason for
this is that the serifs (little dangly things that hang off of the
edges of your fonts -- think Times New Roman) typically get blurred out
by monitors using various anti-aliasing techniques. If you don't
believe me, or if you don't think that doing something as simple as
changing your font can make a big difference on readability,
comprehension, and retention, you might want to check out some of these
studies (there are some great tips about use of color, capital letters,
etc. there too):
Resources
Text Display Readability Work
Contrast Measures for Predicting Text Readability
A Comparison of Popular Online Fonts: Which is Best and When?
Improve the readability of your web pages
Leaf Digital Graphic Design
Best Typefaces for On-screen Readability
Text, Fonts and Readability
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