Adventures In Space: Optical Kerning

August 08, 2016 by Yves Peters

In the spirit of summer blockbusters, I am adding a sequel to my Adventures In Space series. In the second part, about kerning, I mentioned the Optical Kerning setting in Adobe Illustrator. It can improve the spacing of amateur fonts or some typefaces in large display sizes, but – because it ignores the careful manual spacing and kerning of any typeface by a pro-level designer – the setting often creates more problems than it solves. Below are three instances where it will definitely not work. And yes, I am writing this post because I have been there too, scrutinising my screen and wracking my mind trying to figure out why the text looks off. And then go “Argh, of course! Optical kerning…”

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.

Connected Scripts

Because the Optical Kerning algorithm makes no distinction between the actual character and connecting parts or swashes when it recalculates the space between glyphs, the connections are scrambled. I only highlighted the most egregious mistakes, but when you examine the text from up close you will see that almost every single connection is corrupted. To better visualise what happened I alternated the colours between letters. OpenType features automatically replaced the ‘nt’ and ‘pt’ pairs with ligatures. Typeface: [Wishes Script](/families/wishes-script) by [Sabrina Mariela Lopez](/designers/sabrina-mariela-lopez) — Because the Optical Kerning algorithm makes no distinction between the actual character and connecting parts or swashes when it recalculates the space between glyphs, the connections are scrambled. I only highlighted the most egregious mistakes, but when you examine the text from up close you will see that almost every single connection is corrupted. To better visualise what happened I alternated the colours between letters. OpenType features automatically replaced the ‘nt’ and ‘pt’ pairs with ligatures. Typeface: Wishes Script by Sabrina Mariela Lopez

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

The two lines above are identical, the only difference being that the setting for Kerning in the bottom line was switched from Auto to Optical. In some typefaces the alignment errors may be more subtle. Typeface: [Sutro Shaded](/families/sutro) by [Jim Parkinson](/designers/jim-parkinson) — The two lines above are identical, the only difference being that the setting for Kerning in the bottom line was switched from Auto to Optical. In some typefaces the alignment errors may be more subtle. Typeface: Sutro Shaded by Jim Parkinson

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:

Type Trends: Polychromatic Type, an introduction to chromatic typefaces
Polychromatic Type: Dressing in Layers, a tutorial on how to use chromatic typefaces

Monospaced Fonts

When applying Optical Kerning to the monospaced typeface [FF Nuvo® Mono](/families/ff-nuvo-mono) the fixed-width rhythm of the characters in the top line gets lost as the spacing is dramatically altered. If you compare the middle line to the proportional version [FF Nuvo®](/families/ff-nuvo) at the bottom, the awkward combination of monospaced character shapes with proportional spacing is neither fish nor flesh. Typeface: [FF Nuvo®](/superfamilies/ff-nuvo) by [Siegfried Rückel](/designers/siegfried-rueckel) — When applying Optical Kerning to the monospaced typeface FF Nuvo® Mono the fixed-width rhythm of the characters in the top line gets lost as the spacing is dramatically altered. If you compare the middle line to the proportional version FF Nuvo® at the bottom, the awkward combination of monospaced character shapes with proportional spacing is neither fish nor flesh. Typeface: FF Nuvo® by Siegfried Rückel

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.

Adventures in Space

Part 1 – Adventures in Space: Spacing
Part 2 – Adventures in Space: Kerning
Part 2.5 – Adventures in Space: Special Cases
Part 3 – Adventures in Space: Tracking
Part 4 – Adventures in Space: Spaces
Epilogue – Adventures in Space: Optical Kerning

_{Typeface in header image: Hopeless Diamond by Jonathan Barnbrook and Marcus Leis Allion}