KERNING pg. 102

When do you when to use optical kerning or metric kerning?

According to the book, when you select metric kerning you are using the spacing that was intended by the type designer. Designers apply metric kerning to text and this looks good at small sizes. On the other hand optical kerning assesses the shapes of all characters and adjusts the spacing wherever needed. This is good when applied to headlines and when a font has few or no built-in kern pairs, or when the overall spacing seems uneven. Designers suggest using optical kerning when you are combining different fonts or type sizes. So how do you know which kerning to use when formatting text? This depends on your typeface, and it should determine which of the two to use, “it’s a visual thing.”

http://www.creativepro.com/blog/typetalk-metrics-versus-optical-kerning