Optical Kerning sounds so nice and I think that’s one of the reasons people choose to use it. Maybe we could propose that Adobe change it to read Robot Kerning instead. So what exactly does it do? Instead of using the built-in spacing and kerning, the Optical Kerning setting in Adobe Illustrator analyses the shapes of the characters, and then calculates the distance between each pair of glyphs to achieve what it considers optimal spacing. Theoretically this could produce acceptable results in most cases. However there are three specific typographic genres where the results are guaranteed to be disastrous.
The name says it all – the individual letters of connecting scripts link up thanks to connecting strokes that are an integral part of the character shapes. The Optical Kerning algorithm looks at the entire letter form as an abstract concept, without knowing what the function is of each part of the glyph. It doesn’t know if a stroke is supposed to connect with the next letter. It just analyses what is black or white, and there has to be enough white between two successive black shapes. So the Optical Kerning will add space between every two characters, exactly the opposite of what the type designer intended.
Chromatic typefaces have glyphs consisting of shapes that can be layered in different colours. Once the typeface designer has finished drawing and spacing the typeface, she duplicates the font as many times as there are layers. Each glyph then gets disassembled into its separate components, and the elements for each layer are assigned to the different ‘weights’ of the typeface. Next to the font with the base characters there can be a supplementary font with a drop shadow for each glyph, or several fonts with decorative elements that fit inside each glyph, or any other combination. To compose text in a chromatic typeface, you start by setting the text in one of the weights and assign it a colour. Then you duplicate your text box for as many layers as you need, assign different colours to the text in those text boxes, and position the duplicate text boxes exactly on top of each other.
As the different elements of the characters are like pieces of a puzzle, all the layers need to be positioned on top of each other with utmost precision. Yet each layer has an incomplete version of each character. Because pieces are missing, Optical Kerning will analyse the shape of incomplete characters. This can produce wildly varying spacing for each layer of text, with mismatching components of the letters as a result.
See also these two posts by David Sudweeks:
Like I explained at the end of Adventures in Space: Spacing, the structure of monospaced or fixed-width fonts is very different from proportional typefaces. Because every character has to occupy the same horizontal space, narrow letters are stretched and wide letters condensed. Because no spacing needs to be corrected, no kerning has been applied to monospaced fonts. So if Optical Kerning is switched on, the rearrangement of spacing between the characters will negate the monospaced aspect of the characters. In combination with the unusual structure of many letters this will make your text look very wrong.
I think this truly concludes my series Adventures In Space. Did I forget anything? Feel free to get in touch with me with your suggestions.
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