Originally Posted by tony

Here's a way to test the reading ease and comfort of all caps compared to upper and lower case.

Print a one-line sentence in all caps.

Print another in upper and lower case.

Cover the bottom half of the all caps line first with a sheet of paper. Be fair about it and try to make it as close to covering the bottom half of the letters as possible.

Have somebody read that and note the difficulty in being able to discern the words.

Then do the same with upper and lower. Reading will be easier and quicker.

Researchers have found that we read quickly and comfortably by passing our vision over the tops of letters. The tops of all caps are more difficult to discern than the tops of upper and lower. Reading all-caps lines requires we go slowly, and study.

It doesn't matter about the type size. Thats a whole other issue. Its more related to type case: If somebody has poor vision and is trying to read all-caps they will be frustrated.