The effect is similar to morphing, as a designer can choose an intermediate between two styles, for example generating a semibold font by compromising between a bold and regular style, or perhaps extend a trend to create an ultra-light or ultra-bold.
The intention was that using multiple master fonts, a designer can generate a style of the exact width, thickness and optical size wanted, without losing the integrity or readability of the character glyphs. Multiple master fonts contain two or more 'masters'-that is, original font styles-and enable a user to interpolate between these masters along a continuous range of 'axes.' With proper application support, these axes could be adjusted on demand. Multiple master fonts (or MM fonts) are an extension to Adobe Systems' Type 1 PostScript fonts, now superseded by the advent of OpenType and, in particular, the introduction of OpenType Font Variations in OpenType 1.8, also called variable fonts.
