and cause them to struggle to concentrate on the other, much thinner strokes that define which letter is which. For this reason, using the right optical size of digital font has been described as particularly essential with Didone designs. Fonts to be used at text sizes will be sturdier designs with thicker 'thin' strokes and serifs (less stroke contrast) and more space between letters than on display designs, to increase legibility. Optical sizes were a natural requirement of printing technology at the time of Didone typefaces' first creation in metal type, since each size of metal type would be custom-cut, but declined as the pantograph, phototypesetting and digital fonts made printing the same font at any size simpler; a revival has taken place in recent years. French designer Loïc Sander has suggested that the dazzle effect may be particularly common in designs produced in countries where designers are unfamiliar with how to use them effectively and may choose Didone fonts designed for headings. Many modern Didone digital revivals intended for professional printing, such as Parmagiano, ITC Bodoni and Hoefler & Frere-Jones' Didot and Surveyor, have a range of optical sizes, but this is less common on default computer fonts. Among default Didone fonts on computer systems, Century Schoolbook on Windows is oriented towards body text use, while the Didot revival on OS X was specifically intended for display use and not for body text. Derivatives The shape of nineteenth-century Didone designs, with their narrow apertures, has been suggested as a major influence on many early sans-serif fonts such as Akzidenz-Grotesk and its derivatives such as Helvetica, developed in Europe some years after their introduction. An example of this influence is the narrow apertures of these designs, in which strokes on letters such as a and c fold up to become vertical, similar to what is seen on Didone serif fonts. Matthew Carter's Scotch Roman-inspired computer font Georgia is notable as an extremely distant descendant of Didone typefaces. In Georgia, the stroke contrast is greatly reduced and the bold made much bolder than normal in order for the design to render well on a low-resolution computer monitor, but the general letter shape and ball terminals of Scotch Roman designs are preserved. He also developed the Scotch Roman revival Miller for print use. Given these unusual design decisions, Matthew Butterick, an expert on document design, recommended that organizations using Georgia for onscreen