Difference in glyphs of I and l

Question

In many fonts I come across, I see that the glyph uppercase i - I is same as lowercase l.

Why is it so? Why don't font designers add a differentiating factor between the two glyphs?

This specially creates a problem with the word 'Ill'. Whether to read it roman 3 or short for 'I will'.

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Extra

I am asking this because I am making a font, so I want to know if I should stick to this standard design, or use different glyphs for the two... Also, see my last question on fonts as well.

P.S. I don't know if this should goto SuperUser, but I can't post questions there.

Answer 1

Many modern fonts to address this problem. Take Adobe's Source Sans Pro and the example they give:

This shows you how people will differentiate the characters (1, I, and l) that tend to be confused. Just before that image in the article, the author noted:

For usages where this level of distinction is not required, there is an alternate, simple lowercase l (without the tail) accessible via stylistic alternates or by applying a stylistic set.

So you can do both approaches in your font if you'd like!

I don't really have a good answer as to "why is it so" in the first place, though. Typefaces reflect, to a certain extent, either the conventions of handwriting or the conventions of fonts that came before them. Sans-serif developed after serif fonts. So, if you can picture taking your typical serif's I, l, and 1

and removing the serifs, and you get straight lines. That's not a scientifically researched answer, but it's a plausible one to me.

Answer 2

They are not the same. Most of the time the capital height is different than the ascender height. Some letters look the same in small sizes. But this isn't a problem for a text letter since the human mind read words as a whole and not every letter by itself.

"Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteers be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe."

'Ill' won't ever be a problem because you read the whole word and it will in context.

Letters that look alike are only a problem if you want to make a special purpose font (passwords, license plates or for writing code). Than the exact letter matters and all letters should be distinctive. Monospaced letters are used for code: Ii1L and 0oO. Some password generators leave these letters out.

This is a minor problem. Just start designing your font.

Answer 3

First off, lots of typeface do have differences between I, l and 1— the Courier New of these examples proves that point.

In case of the typefaces that don't, or have very subtle differences, the actual answer to your question seems: because it rarely matters. Apparently, it's seldom the case that we are unable to glean from context what glyph is meant. Yes, there are cases like 'Ill', but these don't pop up often enough to impair meaning. Too much.