Greetings!

I'm trying to learn about typefaces - I'm currently designing a book for print, and I hope it won't be my last shot at typography. There's one piece of information I can't seem to find in google: what's the practical difference between Light and Regular font weights? I'm trying to understand whether or not it's all right to use Light in print, and how it works with different font sizes (is it "light for 6-8 pt, regular for 9-14" or "regular for 9-14, light for 15+"?) Can you help me figure this out?

Attached samples: Warnock Pro (Regular and Light), 10pt, Cyrillic (Russian).

Thanks in advance!

… what's the practical difference between Light and Regular font weights?

​Don’t read too much into those style names. There are a rather artificial scale to name different stroke widths. But there is no agreement on what boldness a certain style name should have or how that style would then be used. Those names can even be conflicting, e.g. for one typeface “regular” is bolder than “book” and for another it’s the other way around. 

So long story short: You need to pick the right style depending on your specific project. For a book for example, the paper type and printing technology affect strongly how the type actually appears and how legible it is. Also the point size makes a big difference. A light style might work great for headlines (because it appears more elegant), but might get too light the smaller you set it. 

Edited July 1, 201510 yr by Ralf Herrmann

Here is an interesting article about the subject from a type designers’ perspective, which also explains the historic roots of style names:

http://bigelowandholmes.typepad.com/bigelow-holmes/2015/07/on-font-weight.html

Thank you! That's a very helpful research. Looks like it all really depends on the printing method as opposed to the text characteristics. I'll probably go with Normal this time, it seems pretty balanced in that particular font.

It's partucularly intruguing as another example of how we carry over hundreds of years old technological specifications into our modern-day design conventions.