[Athen] Text readability: can you tell the difference between "rn" and "m"?

[Christine Robinson]

Hi all -

I've been thinking a lot about readability of text, and I'd like to invite you to brainstorm with me. This is a long detailed posting, and it won't hurt my feelings if you delete it here. *smiles* But if you're a curious person like me...
We're likely all familiar with the general guidelines for readable digital text: use a sans serif font like Verdana, use good color contrast and font size, etc.
Lately I've been puzzling over the space between letters, and how typeface choice affects that:
rn m     Il1        Arial
rn m      Il1           Myriad Pro
rn m     Il1        Times New Roman
rn m   Il1      Verdana
(Hopefully this doesn't come across to you converted into plain text; if you don't see the above as different fonts, you may want to play around with it yourself.)
My vision is 20/20, but I find that in most cases, the two lowercase letters RN, next to each other, are difficult to distinguish from the single lowercase letter M. Depending on the typeface, it at times it's also difficult to tell the difference between uppercase I, lowercase L, and/or the numeral 1. Usually I can tell the difference from context, but if it's an unfamiliar word, someone's name, or a password, it may take me a few moments to make sure I'm reading it correctly. Same goes for the common abbreviation for accessibility: a11y.
Fiddling around for better readability, I've tried playing with kerning, increasing the space between letters. Again, if you get this converted to plain text, you won't see that in the text below, I've increased the space between letters by 1 pt:
rn m   Il1      Arial
rn m    Il1       Myriad Pro
rn m   Il1      Times New Roman
rn m Il1    Verdana
It doesn't help with the "uppercase-I, lowercase-L, or numeral 1?" question. It usually helps with the "rn or m?" question, but as a trainer, I can just imagine myself trying to tell people to increase their kerning in order to improve readability. Besides, I don't recall seeing that recommended anywhere as a best practice for digital accessibility.
So I got to thinking, what about monospaced (fixed width) typefaces? The characters each occupy the same amount of horizontal space, unlike the other typefaces above with are variable width.
rn m  Il1   Consolas (monospaced)
rn m   Il1      DejaVu Sans (monospaced)
rn m Il1  Letter Gothic (monospaced)
rn m Il1  Lucida Console (monospaced)
To my eyes, it's usually easier to distinguish between the characters, and I'm tempted to start recommending that people use a typeface like Consolas or Lucida Console. However, again, I don't recall hearing any accessibility people recommending monospaced typefaces.
Anybody have any thoughts on this?
Best,
Chris

Christine Robinson | Technical Trainer/Writer | Center for Teaching Excellence
Georgia Gwinnett College | 1000 University Center Lane, L-2158 | Lawrenceville, GA 30043
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