TypeTalk: Optical Kerning and Scaling Surprises

Q. From what I can tell, Adobe Illustrator's Optical Kerning feature is adding space at the smaller font sizes to keep the spacing between letters distinct. My problem with this is that it changes layouts, rags, etc., but "scaling in proportion" by definition isn't supposed to change anything except for the overall size. Auto Kerning (or Metrics, in InDesign) doesn't cause the same problem.

A. You're an acute observer. What you call a problem is actually a rather sophisticated feature of Adobe InDesign and Illustrator, but unless you know about it and how it behaves in certain situations, it certainly can become a problem! Read on...

(taken from an email sent by The Type Studio)