An example of local correction, but it's not automatic: \definecharacterkerning[narrow][factor=-.02] \definecharacterkerning[wide][factor=.02] \definefontfeature[frac][frac=yes] \def\Narrow#1{\bgroup\setcharacterkerning[narrow]#1\egroup} \def\Wide#1{\bgroup\setcharacterkerning[wide]#1\egroup} \def\NoKerning#1{\bgroup\resetcharacterkerning #1\egroup} \starttext \feature[+][frac]% Some ligatures: float, finance, affine; a fraction: 1/4. \blank Modified kerning: \Narrow{Some ligatures: float, finance, affine; a fraction: 1/4.} \Wide{Some ligatures: float, finance, affine; a fraction: 1/4.} \blank Same as above, but locally corrected: \Narrow{Some ligatures: \NoKerning{fl}oat, \NoKerning{fi}nance, a\NoKerning{ffi}ne; a fraction: \NoKerning{1/4}.} \Wide{Some ligatures: \NoKerning{fl}oat, \NoKerning{fi}nance, a\NoKerning{ffi}ne; a fraction: \NoKerning{1/4}.} \stoptext PS: (errata corrige)
"1", "/", "4" => "ΒΌ" glyph (with "frac" feature switched on)
"1", "/", "4" => "smaller 1" glyph moved up, fraction line glyph, "smaller 4" glyph moved left and down