MINIMUM FONT SIZE FOR READABILITY?

[Geoff Hart <ghart -at- videotron -dot- ca>]

Anna Langley wondered: <<Can you point me to any research proving that 
printed text should not fall below a minimum font size? I've read some 
articles stating font size shouldn't go below 9 point for printed text. 
Other articles state it's a matter of page size.>>

Readability involves a combination of much more than type and page 
size: it depends strongly on the typeface, leading, character and word 
spacing, and a batch of other variables, all of which interact 
promiscuously. So don't look for a single answer; it'll almost 
certainly be wrong for your specific situation. One thing I have seen 
repeatedly in the research is that your minimum font size should 
increase if you have a significant portion of older folks in your 
audience. I'm not yet "elderly", but I generally find 9 point Times on 
the small side of readable, but that's just one data point.

<<I'd like to make a case for increasing the minimum font size to 
improve readability, but I need research to back up my case.>>

Why not do your own research? In a similar situation, I produced three 
versions of the same page using 9-, 10-, and 11-point type that were 
otherwise identical apart from increasing the leading proportionally. 
(PageMaker, autoleading.) I then took these pages around to a bunch of 
"typical readers" in my audience (in this case, forestry researchers 
who were reading a technical report destined for other forestry 
researchers) and polled them: Which page design do you find easiest to 
read?

As noted above, the older folks preferred larger type, but overall, the 
11-point text won handily. Your mileage may vary, of course (depending 
on whether you use leaded or unleaded type? <gdrlh>), but the test 
provides far more convincing data than any journal article because (a) 
it uses your own design, not some wholly unrelated design, and (b) the 
experiences of people you know always seem more "real" than those of an 
anonymous group of test subjects.

--Geoff Hart   ghart -at- videotron -dot- ca
(try geoffhart -at- mac -dot- com if you don't get a reply)