Limitations on choices of Typeface in Prism Mac.

When you choose a font for text in Prism, you can choose any TrueType font. In the Font Panel, you can choose both a Font Family (i.e. Arial) and a Typeface (i.e. regular or bold). 

Prism only recognizes four standard Typefaces: "Regular", "Italic", "Bold", and "Bold Italic". That's it. If you choose a Typeface such as "Medium", "Condensed Black", "Semibold", "Light" or "Ultralight" Prism will use one of the four standard typefaces. Most fonts don't offer more than those four, but some newer fonts do.